diff --git a/app/controllers/api/v1/accounts/conversations_controller.rb b/app/controllers/api/v1/accounts/conversations_controller.rb
index ec107dfff..10a676738 100644
--- a/app/controllers/api/v1/accounts/conversations_controller.rb
+++ b/app/controllers/api/v1/accounts/conversations_controller.rb
@@ -142,6 +142,8 @@ class Api::V1::Accounts::ConversationsController < Api::V1::Accounts::BaseContro
     # and deprecate the support of passing only source_id as the param
     @contact_inbox ||= ::ContactInbox.find_by!(source_id: params[:source_id])
     authorize @contact_inbox.inbox, :show?
+  rescue ActiveRecord::RecordNotUnique
+    render json: { error: 'source_id should be unique' }, status: :unprocessable_entity
   end
 
   def build_contact_inbox
diff --git a/spec/controllers/api/v1/accounts/conversations_controller_spec.rb b/spec/controllers/api/v1/accounts/conversations_controller_spec.rb
index d012d5f53..f38d9c1bf 100644
--- a/spec/controllers/api/v1/accounts/conversations_controller_spec.rb
+++ b/spec/controllers/api/v1/accounts/conversations_controller_spec.rb
@@ -207,7 +207,7 @@ RSpec.describe 'Conversations API', type: :request do
   describe 'POST /api/v1/accounts/{account.id}/conversations' do
     let(:contact) { create(:contact, account: account) }
     let(:inbox) { create(:inbox, account: account) }
-    let(:contact_inbox) { create(:contact_inbox, contact: contact, inbox: inbox) }
+    let!(:contact_inbox) { create(:contact_inbox, contact: contact, inbox: inbox) }
 
     context 'when it is an unauthenticated user' do
       it 'returns unauthorized' do
@@ -251,6 +251,16 @@ RSpec.describe 'Conversations API', type: :request do
           expect(response_data[:additional_attributes]).to eq(additional_attributes)
         end
 
+        it 'does not create a new conversation if source_id is not unique' do
+          new_contact = create(:contact, account: account)
+
+          post "/api/v1/accounts/#{account.id}/conversations",
+               headers: agent.create_new_auth_token,
+               params: { source_id: contact_inbox.source_id, inbox_id: inbox.id, contact_id: new_contact.id },
+               as: :json
+          expect(response).to have_http_status(:unprocessable_entity)
+        end
+
         it 'creates a conversation in specificed status' do
           allow(Rails.configuration.dispatcher).to receive(:dispatch)
           post "/api/v1/accounts/#{account.id}/conversations",