diff --git a/app/models/user.rb b/app/models/user.rb
index d012a168..7699f2c3 100644
--- a/app/models/user.rb
+++ b/app/models/user.rb
@@ -47,6 +47,8 @@ class User < ApplicationRecord
          :invitable
 
   validates_presence_of :first_name, :last_name
+  validate :unique_email_address?
+
 
   has_one :account, foreign_key: "owner_id", inverse_of: :owner
   belongs_to :organization, class_name: "Account", inverse_of: :users
@@ -74,4 +76,8 @@ def color
   def acronyms
     first_name[0] + last_name[0]
   end
+
+  def unique_email_address?
+    return false if User.where(email: self.email).any?
+  end
 end
diff --git a/spec/models/user_spec.rb b/spec/models/user_spec.rb
index 71fcb290..adc2fc71 100644
--- a/spec/models/user_spec.rb
+++ b/spec/models/user_spec.rb
@@ -96,4 +96,12 @@
       expect(user.acronyms).to eq "AS"
     end
   end
+
+  describe "uniqueness of email" do
+    let!(:existing_user) { create(:user, email: "another@email.com") }
+    it "validates the uniqueness of email" do
+      user = build(:user, email: existing_user.email)
+      expect(user).not_to be_valid
+    end
+  end
 end