diff --git a/plugins/cache-ehcache/src/test/java/org/opensearch/cache/store/disk/EhCacheDiskCacheTests.java b/plugins/cache-ehcache/src/test/java/org/opensearch/cache/store/disk/EhCacheDiskCacheTests.java
index cfa0940101ad1..5ff78367c4d35 100644
--- a/plugins/cache-ehcache/src/test/java/org/opensearch/cache/store/disk/EhCacheDiskCacheTests.java
+++ b/plugins/cache-ehcache/src/test/java/org/opensearch/cache/store/disk/EhCacheDiskCacheTests.java
@@ -53,7 +53,6 @@
 import java.util.function.ToLongBiFunction;
 
 import org.ehcache.PersistentCacheManager;
-import org.ehcache.impl.serialization.StringSerializer;
 
 import static org.opensearch.cache.EhcacheDiskCacheSettings.DISK_LISTENER_MODE_SYNC_KEY;
 import static org.opensearch.cache.EhcacheDiskCacheSettings.DISK_MAX_SIZE_IN_BYTES_KEY;
diff --git a/server/src/main/java/org/opensearch/indices/IndicesRequestCache.java b/server/src/main/java/org/opensearch/indices/IndicesRequestCache.java
index a5226012baa77..3f6f04a8d37f6 100644
--- a/server/src/main/java/org/opensearch/indices/IndicesRequestCache.java
+++ b/server/src/main/java/org/opensearch/indices/IndicesRequestCache.java
@@ -128,11 +128,14 @@ public final class IndicesRequestCache implements RemovalListener<ICacheKey<Indi
     /**
      * If pluggable caching is off, or pluggable caching is on but a store name isn't specified, this setting determines the cache size.
      * Otherwise, the implementation-specific size setting like indices.requests.cache.opensearch_onheap.size is used instead.
+     *
+     * Deprecated; once pluggable caching is no longer behind a feature flag (likely in 2.19), this setting will no longer have any effect.
      */
     public static final Setting<ByteSizeValue> INDICES_CACHE_QUERY_SIZE = Setting.memorySizeSetting(
         "indices.requests.cache.size",
         "1%",
-        Property.NodeScope
+        Property.NodeScope,
+        Property.Deprecated
     );
     public static final Setting<TimeValue> INDICES_CACHE_QUERY_EXPIRE = Setting.positiveTimeSetting(
         "indices.requests.cache.expire",
@@ -229,8 +232,7 @@ CacheConfig<Key, BytesReference> getCacheConfig(Settings settings, NodeEnvironme
         if (!CacheService.pluggableCachingEnabled(CacheType.INDICES_REQUEST_CACHE, settings)) {
             // If pluggable caching is not enabled, use the max size based on the IRC setting into the config.
             // If pluggable caching is enabled, cache implementations instead determine their own sizes based on their own implementation
-            // size
-            // settings.
+            // size settings.
             configBuilder.setMaxSizeInBytes(sizeInBytes);
         }
         return configBuilder.build();
diff --git a/server/src/test/java/org/opensearch/indices/IndicesRequestCacheTests.java b/server/src/test/java/org/opensearch/indices/IndicesRequestCacheTests.java
index 3a2b12bc239b2..e83ca247b6a1d 100644
--- a/server/src/test/java/org/opensearch/indices/IndicesRequestCacheTests.java
+++ b/server/src/test/java/org/opensearch/indices/IndicesRequestCacheTests.java
@@ -868,6 +868,7 @@ public void testCacheMaxSize_WhenPluggableCachingOff() throws Exception {
             config = cache.getCacheConfig(settings, env);
         }
         assertEquals(cacheSize, (long) config.getMaxSizeInBytes());
+        allowDeprecationWarning();
     }
 
     public void testCacheMaxSize_WhenPluggableCachingOn() throws Exception {
@@ -888,6 +889,7 @@ public void testCacheMaxSize_WhenPluggableCachingOn() throws Exception {
             config = cache.getCacheConfig(settings, env);
         }
         assertEquals(0, (long) config.getMaxSizeInBytes());
+        allowDeprecationWarning();
     }
 
     private IndicesRequestCache getIndicesRequestCache(Settings settings) throws IOException {
@@ -1133,6 +1135,7 @@ public void testEviction() throws Exception {
         assertEquals(2, cache.count());
         assertEquals(1, indexShard.requestCache().stats().getEvictions());
         IOUtils.close(reader, secondReader, thirdReader, environment);
+        allowDeprecationWarning();
     }
 
     public void testClearAllEntityIdentity() throws Exception {
@@ -1410,6 +1413,7 @@ public void testGetOrComputeConcurrentlyWithMultipleIndices() throws Exception {
         }
         IOUtils.close(cache);
         executorService.shutdownNow();
+        allowDeprecationWarning();
     }
 
     public void testDeleteAndCreateIndexShardOnSameNodeAndVerifyStats() throws Exception {
@@ -1578,6 +1582,12 @@ public static String generateString(int length) {
         return sb.toString();
     }
 
+    private void allowDeprecationWarning() {
+        assertWarnings(
+            "[indices.requests.cache.size] setting was deprecated in OpenSearch and will be removed in a future release! See the breaking changes documentation for the next major version."
+        );
+    }
+
     private class TestBytesReference extends AbstractBytesReference {
 
         int dummyValue;