diff --git a/libraries/Microsoft.Bot.Schema/Attachment.cs b/libraries/Microsoft.Bot.Schema/Attachment.cs
index a4291ba006..b89d102cfa 100644
--- a/libraries/Microsoft.Bot.Schema/Attachment.cs
+++ b/libraries/Microsoft.Bot.Schema/Attachment.cs
@@ -3,6 +3,7 @@
 
 namespace Microsoft.Bot.Schema
 {
+    using Microsoft.Bot.Schema.Converters;
     using Newtonsoft.Json;
     using Newtonsoft.Json.Linq;
 
@@ -53,6 +54,7 @@ public Attachment(string contentType = default, string contentUrl = default, obj
         /// </summary>
         /// <value>The embedded content.</value>
         [JsonProperty(PropertyName = "content")]
+        [JsonConverter(typeof(AttachmentMemoryStreamConverter))]
         public object Content { get; set; }
 
         /// <summary>
diff --git a/libraries/Microsoft.Bot.Schema/Converters/AttachmentMemoryStreamConverter.cs b/libraries/Microsoft.Bot.Schema/Converters/AttachmentMemoryStreamConverter.cs
new file mode 100644
index 0000000000..8667bd215f
--- /dev/null
+++ b/libraries/Microsoft.Bot.Schema/Converters/AttachmentMemoryStreamConverter.cs
@@ -0,0 +1,196 @@
+// Copyright (c) Microsoft Corporation. All rights reserved.
+// Licensed under the MIT License.
+
+using System;
+using System.Collections;
+using System.Collections.Generic;
+using System.IO;
+using System.Linq;
+using Newtonsoft.Json;
+using Newtonsoft.Json.Linq;
+using Newtonsoft.Json.Serialization;
+
+namespace Microsoft.Bot.Schema.Converters
+{
+    /// <summary>
+    /// Converter which allows a MemoryStream instance to be used during JSON serialization/deserialization.
+    /// </summary>
+#pragma warning disable CA1812 // Avoid uninstantiated internal classes.
+    internal class AttachmentMemoryStreamConverter : JsonConverter
+    {
+        public override bool CanConvert(Type objectType)
+        {
+            return typeof(MemoryStream).IsAssignableFrom(objectType);
+        }
+
+        /// <returns>
+        ///     If the object is of type:<br/>
+        ///     <list type="table">
+        ///         <item>
+        ///             <b>List/Array</b>
+        ///             <list type="bullet">
+        ///                 <item><i>Without MemoryStream</i>: it will return a JArray.</item>
+        ///                 <item><i>With MemoryStream</i>: it will return a List.</item>
+        ///             </list>            
+        ///         </item>
+        ///         <item>
+        ///             <b>Dictionary/Object</b>
+        ///             <list type="bullet">
+        ///                 <item><i>Without MemoryStream</i>: it will return a JObject.</item>
+        ///                 <item><i>With MemoryStream</i>: it will return a Dictionary.</item>
+        ///             </list>            
+        ///         </item>
+        ///     </list>
+        /// </returns>
+        /// <inheritdoc/>
+        public override object ReadJson(JsonReader reader, Type objectType, object existingValue, JsonSerializer serializer)
+        {
+            if (reader.TokenType == JsonToken.Null)
+            {
+                return JValue.CreateNull();
+            }
+
+            if (reader.TokenType == JsonToken.StartArray)
+            {
+                var list = new List<object>();
+                reader.Read();
+                while (reader.TokenType != JsonToken.EndArray)
+                {
+                    var item = ReadJson(reader, objectType, existingValue, serializer);
+                    list.Add(item);
+                    reader.Read();
+                }
+
+                if (HaveStreams(list))
+                {
+                    return list;
+                }
+                else
+                {
+                    return JArray.FromObject(list);
+                }
+            }
+
+            if (reader.TokenType == JsonToken.StartObject)
+            {
+                var deserialized = serializer.Deserialize<JToken>(reader);
+
+                var isStream = deserialized.Type == JTokenType.Object && deserialized.Value<string>("$type") == nameof(MemoryStream);
+                if (isStream)
+                {
+                    var stream = deserialized.ToObject<SerializedMemoryStream>();
+                    return new MemoryStream(stream.Buffer.ToArray());
+                }
+
+                var newReader = deserialized.CreateReader();
+                newReader.Read();
+                string key = null;
+                var dict = new Dictionary<string, object>();
+                while (newReader.Read())
+                {
+                    if (newReader.TokenType == JsonToken.EndObject)
+                    {
+                        continue;
+                    }
+
+                    if (newReader.TokenType == JsonToken.PropertyName)
+                    {
+                        key = newReader.Value.ToString();
+                        continue;
+                    }
+
+                    var item = ReadJson(newReader, objectType, existingValue, serializer);
+                    dict.Add(key, item);
+                }
+
+                var list = dict.Values.ToList();
+                if (HaveStreams(list))
+                {
+                    return dict;
+                }
+                else
+                {
+                    return JObject.FromObject(dict);
+                }
+            }
+
+            return serializer.Deserialize(reader);
+        }
+
+        public override void WriteJson(JsonWriter writer, object value, JsonSerializer serializer)
+        {
+            if (!typeof(MemoryStream).IsAssignableFrom(value.GetType()))
+            {
+                if (value.GetType().GetInterface(nameof(IEnumerable)) != null)
+                {
+                    // This makes the WriteJson loops over nested values to replace all instances of MemoryStream.
+                    serializer.Converters.Add(this);
+                }
+
+                JToken.FromObject(value, serializer).WriteTo(writer);
+                serializer.Converters.Remove(this);
+                return;
+            }
+
+            var buffer = (value as MemoryStream).ToArray();
+            var result = new SerializedMemoryStream
+            {
+                Type = nameof(MemoryStream),
+                Buffer = buffer.ToList()
+            };
+
+            JToken.FromObject(result).WriteTo(writer);
+        }
+
+        /// <summary>
+        /// Check if a List contains at least one MemoryStream.
+        /// </summary>
+        /// <param name="list">List of values that might have a MemoryStream instance.</param>
+        /// <returns>True if there is at least one MemoryStream in the list, otherwise false.</returns>
+        private static bool HaveStreams(List<object> list)
+        {
+            var result = false;
+            foreach (var nextLevel in list)
+            {
+                if (nextLevel == null)
+                {
+                    continue;
+                }
+
+                if (nextLevel.GetType() == typeof(MemoryStream))
+                {
+                    result = true;
+                }
+
+                // Type generated from the ReadJson => JsonToken.StartObject.
+                if (nextLevel.GetType() == typeof(Dictionary<string, object>))
+                {
+                    result = HaveStreams((nextLevel as Dictionary<string, object>).Values.ToList());
+                }
+
+                // Type generated from the ReadJson => JsonToken.StartArray.
+                if (nextLevel.GetType() == typeof(List<object>))
+                {
+                    result = HaveStreams(nextLevel as List<object>);
+                }
+
+                if (result)
+                {
+                    break;
+                }
+            }
+
+            return result;
+        }
+
+        internal class SerializedMemoryStream
+        {
+            [JsonProperty("$type")]
+            public string Type { get; set; }
+
+            [JsonProperty("buffer")]
+            public List<byte> Buffer { get; set; }
+        }
+    }
+#pragma warning restore CA1812
+}
diff --git a/tests/Microsoft.Bot.Schema.Tests/AttachmentTests.cs b/tests/Microsoft.Bot.Schema.Tests/AttachmentTests.cs
index 783ca6cd8f..bd5b51a64f 100644
--- a/tests/Microsoft.Bot.Schema.Tests/AttachmentTests.cs
+++ b/tests/Microsoft.Bot.Schema.Tests/AttachmentTests.cs
@@ -2,6 +2,10 @@
 // Licensed under the MIT License.
 
 using System.Collections.Generic;
+using System.IO;
+using System.Linq;
+using System.Text;
+using Newtonsoft.Json;
 using Newtonsoft.Json.Linq;
 using Xunit;
 
@@ -98,5 +102,156 @@ public void AttachmentViewInits()
             Assert.Equal(viewId, attachmentView.ViewId);
             Assert.Equal(size, attachmentView.Size);
         }
+
+        [Fact]
+        public void AttachmentShouldWorkWithoutJsonConverter()
+        {
+            var text = "Hi!";
+            var activity = new ActivityDummy
+            {
+                Attachments = new Attachment[]
+                {
+                    new AttachmentDummy { ContentType = "string", Content = text },
+                    new AttachmentDummy { ContentType = "string/array", Content = new string[] { text } },
+                    new AttachmentDummy { ContentType = "dict", Content = new Dictionary<string, object> { { "firstname", "John" }, { "attachment1", new AttachmentDummy(content: text) }, { "lastname", "Doe" }, { "attachment2", new AttachmentDummy(content: text) }, { "age", 18 } } },
+                    new AttachmentDummy { ContentType = "attachment", Content = new AttachmentDummy(content: text) },
+                    new AttachmentDummy { ContentType = "attachment/dict", Content = new Dictionary<string, AttachmentDummy> { { "attachment", new AttachmentDummy(content: text) }, { "attachment2", new AttachmentDummy(content: text) } } },
+                    new AttachmentDummy { ContentType = "attachment/dict/nested", Content = new Dictionary<string, Dictionary<string, AttachmentDummy>> { { "attachment", new Dictionary<string, AttachmentDummy> { { "content", new AttachmentDummy(content: text) } } } } },
+                    new AttachmentDummy { ContentType = "attachment/list", Content = new List<AttachmentDummy> { new AttachmentDummy(content: text), new AttachmentDummy(content: text) } },
+                    new AttachmentDummy { ContentType = "attachment/list/nested", Content = new List<List<AttachmentDummy>> { new List<AttachmentDummy> { new AttachmentDummy(content: text) } } },
+                }
+            };
+
+            AssertAttachment(activity);
+        }
+
+        [Fact]
+        public void AttachmentShouldWorkWithJsonConverter()
+        {
+            var text = "Hi!";
+            var activity = new Activity
+            {
+                Attachments = new Attachment[]
+                {
+                    new Attachment { ContentType = "string", Content = text },
+                    new Attachment { ContentType = "string/array", Content = new string[] { text } },
+                    new Attachment { ContentType = "dict", Content = new Dictionary<string, object> { { "firstname", "John" }, { "attachment1", new Attachment(content: text) }, { "lastname", "Doe" }, { "attachment2", new Attachment(content: text) }, { "age", 18 } } },
+                    new Attachment { ContentType = "attachment", Content = new Attachment(content: text) },
+                    new Attachment { ContentType = "attachment/dict", Content = new Dictionary<string, Attachment> { { "attachment", new Attachment(content: text) } } },
+                    new Attachment { ContentType = "attachment/dict/nested", Content = new Dictionary<string, Dictionary<string, Attachment>> { { "attachment", new Dictionary<string, Attachment> { { "content", new Attachment(content: text) } } } } },
+                    new Attachment { ContentType = "attachment/list", Content = new List<Attachment> { new Attachment(content: text), new Attachment(content: text) } },
+                    new Attachment { ContentType = "attachment/list/nested", Content = new List<List<Attachment>> { new List<Attachment> { new Attachment(content: text) } } },
+                }
+            };
+
+            AssertAttachment(activity);
+        }
+
+        [Fact]
+        public void MemoryStreamAttachmentShouldWorkWithJsonConverter()
+        {
+            var text = "Hi!";
+            var buffer = Encoding.UTF8.GetBytes(text);
+            var activity = new Activity
+            {
+                Attachments = new Attachment[]
+                {
+                    new Attachment { ContentType = "stream", Content = new MemoryStream(buffer) },
+                    new Attachment { ContentType = "stream/empty", Content = new MemoryStream() },
+                    new Attachment { ContentType = "stream/dict", Content = new Dictionary<string, MemoryStream> { { "stream", new MemoryStream(buffer) } } },
+                    new Attachment { ContentType = "stream/dict/nested", Content = new Dictionary<string, Dictionary<string, MemoryStream>> { { "stream", new Dictionary<string, MemoryStream> { { "content", new MemoryStream(buffer) } } } } },
+                    new Attachment { ContentType = "stream/list", Content = new List<MemoryStream> { new MemoryStream(buffer), new MemoryStream(buffer) } },
+                    new Attachment { ContentType = "stream/list/nested", Content = new List<List<MemoryStream>> { new List<MemoryStream> { new MemoryStream(buffer) } } },
+                }
+            };
+
+            var serialized = JsonConvert.SerializeObject(activity, new JsonSerializerSettings { MaxDepth = null });
+            var deserialized = JsonConvert.DeserializeObject<Activity>(serialized);
+
+            var buffer0 = (GetAttachmentContentByType(deserialized, "stream") as MemoryStream).ToArray();
+            var buffer1 = (GetAttachmentContentByType(deserialized, "stream/empty") as MemoryStream).ToArray();
+            var buffer2 = ((GetAttachmentContentByType(deserialized, "stream/dict") as Dictionary<string, object>)["stream"] as MemoryStream).ToArray();
+            var buffer3 = (((GetAttachmentContentByType(deserialized, "stream/dict/nested") as Dictionary<string, object>)["stream"] as Dictionary<string, object>)["content"] as MemoryStream).ToArray();
+            var buffer4 = ((GetAttachmentContentByType(deserialized, "stream/list") as List<object>)[0] as MemoryStream).ToArray();
+            var buffer4_1 = ((GetAttachmentContentByType(deserialized, "stream/list") as List<object>)[1] as MemoryStream).ToArray();
+            var buffer5 = (((GetAttachmentContentByType(deserialized, "stream/list/nested") as List<object>)[0] as List<object>)[0] as MemoryStream).ToArray();
+
+            Assert.Equal(text, Encoding.UTF8.GetString(buffer0));
+            Assert.Equal(buffer, buffer0);
+            Assert.Equal([], buffer1);
+            Assert.Equal(buffer, buffer2);
+            Assert.Equal(buffer, buffer3);
+            Assert.Equal(buffer, buffer4);
+            Assert.Equal(buffer, buffer4_1);
+            Assert.Equal(buffer, buffer5);
+        }
+
+        [Fact]
+        public void MemoryStreamAttachmentShouldFailWithoutJsonConverter()
+        {
+            var text = "Hi!";
+            var buffer = Encoding.UTF8.GetBytes(text);
+            var activity = new ActivityDummy
+            {
+                Attachments = new Attachment[]
+                {
+                    new AttachmentDummy { ContentType = "stream", Content = new MemoryStream(buffer) },
+                }
+            };
+
+            var ex = Assert.Throws<JsonSerializationException>(() => JsonConvert.SerializeObject(activity, new JsonSerializerSettings { MaxDepth = null }));
+            Assert.Contains("ReadTimeout", ex.Message);
+        }
+
+        private void AssertAttachment<T>(T activity)
+            where T : Activity
+        {
+            var serialized = JsonConvert.SerializeObject(activity, new JsonSerializerSettings { MaxDepth = null });
+            var deserialized = JsonConvert.DeserializeObject<T>(serialized);
+
+            var attachment0 = GetAttachmentContentByType(deserialized, "string") as string;
+            var attachment1 = (GetAttachmentContentByType(deserialized, "string/array") as JArray).First.Value<string>();
+            var attachment2 = GetAttachmentContentByType(deserialized, "dict") as JObject;
+            var attachment3 = (GetAttachmentContentByType(deserialized, "attachment") as JObject).Value<string>("content");
+            var attachment4 = (GetAttachmentContentByType(deserialized, "attachment/dict") as JObject).GetValue("attachment").Value<string>("content");
+            var attachment5 = ((GetAttachmentContentByType(deserialized, "attachment/dict/nested") as JObject).GetValue("attachment") as JObject).GetValue("content").Value<string>("content");
+            var attachment6 = (GetAttachmentContentByType(deserialized, "attachment/list") as JArray)[0].Value<string>("content");
+            var attachment6_1 = (GetAttachmentContentByType(deserialized, "attachment/list") as JArray)[1].Value<string>("content");
+            var attachment7 = (GetAttachmentContentByType(deserialized, "attachment/list/nested") as JArray).First.First.Value<string>("content");
+
+            var expectedString = GetAttachmentContentByType(activity, "string") as string;
+            var expectedDict = GetAttachmentContentByType(activity, "dict") as Dictionary<string, object>;
+            Assert.Equal(expectedString, attachment0);
+            Assert.Equal(expectedString, attachment1);
+            Assert.Equal($"{expectedDict["firstname"]} {expectedDict["lastname"]} {expectedDict["age"]}", $"{attachment2["firstname"]} {attachment2["lastname"]} {attachment2["age"]}");
+            Assert.Equal(expectedString, attachment3);
+            Assert.Equal(expectedString, attachment4);
+            Assert.Equal(expectedString, attachment5);
+            Assert.Equal(expectedString, attachment6);
+            Assert.Equal(expectedString, attachment6_1);
+            Assert.Equal(expectedString, attachment7);
+        }
+
+        private object GetAttachmentContentByType<T>(T activity, string contenttype)
+            where T : Activity
+        {
+            var attachment = activity.Attachments.First(e => e.ContentType == contenttype);
+            return attachment.Content ?? (attachment as AttachmentDummy).Content;
+        }
+
+        public class ActivityDummy : Activity
+        {
+        }
+
+        public class AttachmentDummy : Attachment
+        {
+            public AttachmentDummy(object content = default)
+            {
+                Content = content;
+            }
+
+            [JsonProperty(PropertyName = "content")]
+            public new object Content { get; set; }
+        }
     }
 }