diff --git a/src/Service.gs b/src/Service.gs
index cedde21..72a2b59 100644
--- a/src/Service.gs
+++ b/src/Service.gs
@@ -101,6 +101,16 @@ Service_.prototype.setMethod = function(method) {
   return this;
 };
 
+/**
+ * Sets the OAuth realm parameter to be used with this service (optional).
+ * @param {string} realm The realm to be used with this service.
+ * @return {Service_} This service, for chaining.
+ */
+Service_.prototype.setRealm = function(realm) {
+  this.realm_ = realm;
+  return this;
+};
+
 /**
  * Sets the OAuth signature method to use. 'HMAC-SHA1' is the default.
  * @param {string} signatureMethod The OAuth signature method. Allowed values
@@ -415,6 +425,9 @@ Service_.prototype.fetchInternal_ = function(url, params, opt_token,
     request.data = data;
   }
   oauthParams = signer.authorize(request, token, oauthParams);
+  if (this.realm_ != null) {
+    oauthParams.realm = this.realm_;
+  }
   switch (this.paramLocation_) {
     case 'auth-header':
       params.headers = _.extend({}, params.headers,
diff --git a/src/Signer.gs b/src/Signer.gs
index f1285cd..7d3d565 100644
--- a/src/Signer.gs
+++ b/src/Signer.gs
@@ -24,6 +24,7 @@
  * https://github.com/ddo/oauth-1.0a
  * The cryptojs dependency was removed in favor of native Apps Script functions.
  * A new parameter was added to authorize() for additional oauth params.
+ * Support for realm authorization parameter was added in toHeader().
  */
 
 (function(global) {
@@ -267,7 +268,7 @@
     var header_value = 'OAuth ';
 
     for(var key in oauth_data) {
-      if (key.indexOf('oauth_') === -1)
+      if (key !== 'realm' && key.indexOf('oauth_') === -1)
         continue;
       header_value += this.percentEncode(key) + '="' + this.percentEncode(oauth_data[key]) + '"' + this.parameter_seperator;
     }