diff --git a/core/packages/gax/src/transcoding.ts b/core/packages/gax/src/transcoding.ts
index 37b399f50e2e..3f313d8dd65f 100644
--- a/core/packages/gax/src/transcoding.ts
+++ b/core/packages/gax/src/transcoding.ts
@@ -151,14 +151,16 @@ export function encodeWithSlashes(str: string): string {
   return str
     .split('')
     .map(c => (c.match(/[-_.~0-9a-zA-Z]/) ? c : encodeURIComponent(c)))
-    .join('');
+    .join('')
+    .replace(/\.\./g, '%2E%2E');
 }
 
 export function encodeWithoutSlashes(str: string): string {
   return str
     .split('')
     .map(c => (c.match(/[-_.~0-9a-zA-Z/]/) ? c : encodeURIComponent(c)))
-    .join('');
+    .join('')
+    .replace(/\.\./g, '%2E%2E');
 }
 
 function escapeRegExp(str: string) {
diff --git a/core/packages/gax/test/unit/transcoding.ts b/core/packages/gax/test/unit/transcoding.ts
index f6c6669c6bea..813c4bcc796a 100644
--- a/core/packages/gax/test/unit/transcoding.ts
+++ b/core/packages/gax/test/unit/transcoding.ts
@@ -368,6 +368,7 @@ describe('gRPC to HTTP transcoding', () => {
       ),
       '_.~0-9abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ%2F%20',
     );
+    assert.strictEqual(encodeWithSlashes('..'), '%2E%2E');
   });
 
   it('encodeWithoutSlashes', () => {
@@ -382,6 +383,8 @@ describe('gRPC to HTTP transcoding', () => {
       ),
       '_.~0-9abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ/%20',
     );
+    assert.strictEqual(encodeWithoutSlashes('..'), '%2E%2E');
+    assert.strictEqual(encodeWithoutSlashes('..?$httpMethod=DELETE#'), '%2E%2E%3F%24httpMethod%3DDELETE%23');
   });
 
   it('applyPattern', () => {