diff --git a/src/amplitude-client.js b/src/amplitude-client.js
index 701d2934..0a6e8c13 100644
--- a/src/amplitude-client.js
+++ b/src/amplitude-client.js
@@ -44,6 +44,7 @@ var AmplitudeClient = function AmplitudeClient(instanceName) {
   this._sending = false;
   this._updateScheduled = false;
   this._onInit = [];
+  this._onNewSession = [];
 
   // event meta data
   this._eventId = 0;
@@ -172,6 +173,9 @@ AmplitudeClient.prototype.init = function init(apiKey, opt_userId, opt_config, o
         if (this.options.unsetParamsReferrerOnNewSession) {
           this._unsetUTMParams();
         }
+        for (let i = 0; i < this._onNewSession.length; i++) {
+          this._onNewSession[i](this);
+        }
         this._newSession = true;
         this._sessionId = now;
 
@@ -479,6 +483,10 @@ AmplitudeClient.prototype.onInit = function (callback) {
   }
 };
 
+AmplitudeClient.prototype.onNewSessionStart = function (callback) {
+  this._onNewSession.push(callback)
+}
+
 /**
  * Returns the id of the current session.
  * @public