diff --git a/app/lib/client/methods/sendMessage.js b/app/lib/client/methods/sendMessage.js
index 4ba64c0059a7..d765eefe27c7 100644
--- a/app/lib/client/methods/sendMessage.js
+++ b/app/lib/client/methods/sendMessage.js
@@ -1,17 +1,23 @@
 import { Meteor } from 'meteor/meteor';
 import { TimeSync } from 'meteor/mizzao:timesync';
 import s from 'underscore.string';
+import toastr from 'toastr';
 
 import { ChatMessage } from '../../../models';
 import { settings } from '../../../settings';
 import { callbacks } from '../../../callbacks';
 import { promises } from '../../../promises/client';
+import { t } from '../../../utils/client';
 
 Meteor.methods({
 	sendMessage(message) {
 		if (!Meteor.userId() || s.trim(message.msg) === '') {
 			return false;
 		}
+		const messageAlreadyExists = message._id && ChatMessage.findOne({ _id: message._id });
+		if (messageAlreadyExists) {
+			return toastr.error(t('Message_Already_Sent'));
+		}
 		const user = Meteor.user();
 		message.ts = isNaN(TimeSync.serverOffset()) ? new Date() : new Date(Date.now() + TimeSync.serverOffset());
 		message.u = {
diff --git a/app/lib/server/functions/sendMessage.js b/app/lib/server/functions/sendMessage.js
index 290218f14e3d..2cb04ff465cb 100644
--- a/app/lib/server/functions/sendMessage.js
+++ b/app/lib/server/functions/sendMessage.js
@@ -198,6 +198,10 @@ export const sendMessage = function(user, message, room, upsert = false) {
 			}, message);
 			message._id = _id;
 		} else {
+			const messageAlreadyExists = message._id && Messages.findOneById(message._id, { fields: { _id: 1 } });
+			if (messageAlreadyExists) {
+				return;
+			}
 			message._id = Messages.insert(message);
 		}
 
diff --git a/packages/rocketchat-i18n/i18n/en.i18n.json b/packages/rocketchat-i18n/i18n/en.i18n.json
index b9a8ac3c7461..b5955587779b 100644
--- a/packages/rocketchat-i18n/i18n/en.i18n.json
+++ b/packages/rocketchat-i18n/i18n/en.i18n.json
@@ -2010,6 +2010,7 @@
   "Message_AllowSnippeting": "Allow Message Snippeting",
   "Message_AllowStarring": "Allow Message Starring",
   "Message_AllowUnrecognizedSlashCommand": "Allow Unrecognized Slash Commands",
+  "Message_Already_Sent": "This message has already been sent and is being processed by the server",
   "Message_AlwaysSearchRegExp": "Always Search Using RegExp",
   "Message_AlwaysSearchRegExp_Description": "We recommend to set `True` if your language is not supported on <a target=\"_blank\" href=\"https://docs.mongodb.org/manual/reference/text-search-languages/#text-search-languages\">MongoDB text search</a>.",
   "Message_Attachments": "Message Attachments",