diff --git a/README.md b/README.md
index d3dde6ec23..2badb8525a 100755
--- a/README.md
+++ b/README.md
@@ -332,7 +332,7 @@ These are the available config options for making requests. Only the `url` is re
   headers: {'X-Requested-With': 'XMLHttpRequest'},
 
   // `params` are the URL parameters to be sent with the request
-  // Must be a plain object or a AxiosURLSearchParams object
+  // Must be a plain object or a URLSearchParams object
   params: {
     ID: 12345
   },
@@ -346,7 +346,7 @@ These are the available config options for making requests. Only the `url` is re
   // `data` is the data to be sent as the request body
   // Only applicable for request methods 'PUT', 'POST', 'DELETE , and 'PATCH'
   // When no `transformRequest` is set, must be of one of the following types:
-  // - string, plain object, ArrayBuffer, ArrayBufferView, AxiosURLSearchParams
+  // - string, plain object, ArrayBuffer, ArrayBufferView, URLSearchParams
   // - Browser only: FormData, File, Blob
   // - Node only: Stream, Buffer
   data: {
diff --git a/index.d.ts b/index.d.ts
index 1f82f5080d..b98a5c617a 100644
--- a/index.d.ts
+++ b/index.d.ts
@@ -90,22 +90,34 @@ export interface GenericAbortSignal {
 }
 
 export interface FormDataVisitorHelpers {
-  defaultVisitor: FormDataVisitor;
+  defaultVisitor: SerializerVisitor;
   convertValue: (value: any) => any;
   isVisitable: (value: any) => boolean;
 }
 
-export interface FormDataVisitor {
+export interface SerializerVisitor {
   (value: any, key: string | number, path: null | Array<string | number>, helpers: FormDataVisitorHelpers): boolean;
 }
 
-export interface FormSerializerOptions {
-  visitor?: FormDataVisitor;
+export interface SerializerOptions {
+  visitor?: SerializerVisitor;
   dots?: boolean;
   metaTokens?: boolean;
   indexes?: boolean;
 }
 
+// tslint:disable-next-line
+export interface FormSerializerOptions extends SerializerOptions {
+}
+
+export interface ParamEncoder {
+  (value: any, defaultEncoder: (value: any) => any): any;
+}
+
+export interface ParamsSerializerOptions extends SerializerOptions {
+  encode?: ParamEncoder;
+}
+
 export interface AxiosRequestConfig<D = any> {
   url?: string;
   method?: Method | string;
@@ -114,7 +126,7 @@ export interface AxiosRequestConfig<D = any> {
   transformResponse?: AxiosResponseTransformer | AxiosResponseTransformer[];
   headers?: AxiosRequestHeaders;
   params?: any;
-  paramsSerializer?: (params: any) => string;
+  paramsSerializer?: ParamsSerializerOptions;
   data?: D;
   timeout?: number;
   timeoutErrorMessage?: string;
diff --git a/lib/helpers/AxiosURLSearchParams.js b/lib/helpers/AxiosURLSearchParams.js
index f46e8ce6e5..7c49f185f7 100644
--- a/lib/helpers/AxiosURLSearchParams.js
+++ b/lib/helpers/AxiosURLSearchParams.js
@@ -18,7 +18,7 @@ function encode(str) {
 }
 
 function AxiosURLSearchParams(params, options) {
-  this.pairs = [];
+  this._pairs = [];
 
   params && toFormData(params, this, options);
 }
@@ -26,7 +26,7 @@ function AxiosURLSearchParams(params, options) {
 var prototype = AxiosURLSearchParams.prototype;
 
 prototype.append = function append(name, value) {
-  this.pairs.push([name, value]);
+  this._pairs.push([name, value]);
 };
 
 prototype.toString = function toString(encoder) {
@@ -34,7 +34,7 @@ prototype.toString = function toString(encoder) {
     return encoder.call(this, value, encode);
   } : encode;
 
-  return this.pairs.map(function each(pair) {
+  return this._pairs.map(function each(pair) {
     return _encode(pair[0]) + '=' + _encode(pair[1]);
   }, '').join('&');
 };
diff --git a/lib/helpers/buildURL.js b/lib/helpers/buildURL.js
index 2e498f76f0..bebacb3aee 100644
--- a/lib/helpers/buildURL.js
+++ b/lib/helpers/buildURL.js
@@ -1,5 +1,6 @@
 'use strict';
 
+var utils = require('../utils');
 var AxiosURLSearchParams = require('../helpers/AxiosURLSearchParams');
 
 function encode(val) {
@@ -27,11 +28,20 @@ module.exports = function buildURL(url, params, options) {
   }
 
   var hashmarkIndex = url.indexOf('#');
+
   if (hashmarkIndex !== -1) {
     url = url.slice(0, hashmarkIndex);
   }
 
-  url += (url.indexOf('?') === -1 ? '?' : '&') + new AxiosURLSearchParams(params, options).toString(encode);
+  var _encode = options && options.encode || encode;
+
+  var serializerParams = utils.isURLSearchParams(params) ?
+    params.toString() :
+    new AxiosURLSearchParams(params, options).toString(_encode);
+
+  if (serializerParams) {
+    url += (url.indexOf('?') === -1 ? '?' : '&') + serializerParams;
+  }
 
   return url;
 };
diff --git a/test/specs/helpers/buildURL.spec.js b/test/specs/helpers/buildURL.spec.js
index 7adf57449e..0bee3e9a05 100644
--- a/test/specs/helpers/buildURL.spec.js
+++ b/test/specs/helpers/buildURL.spec.js
@@ -17,7 +17,7 @@ describe('helpers::buildURL', function () {
       foo: {
         bar: 'baz'
       }
-    })).toEqual('/foo?foo=' + encodeURI('{"bar":"baz"}'));
+    })).toEqual('/foo?foo[bar]=baz');
   });
 
   it('should support date params', function () {
@@ -60,15 +60,6 @@ describe('helpers::buildURL', function () {
     })).toEqual('/foo?foo=bar&query=baz');
   });
 
-  it('should use serializer if provided', function () {
-    serializer = sinon.stub();
-    params = {foo: 'bar'};
-    serializer.returns('foo=bar');
-    expect(buildURL('/foo', params, serializer)).toEqual('/foo?foo=bar');
-    expect(serializer.calledOnce).toBe(true);
-    expect(serializer.calledWith(params)).toBe(true);
-  });
-
   it('should support URLSearchParams', function () {
     expect(buildURL('/foo', new URLSearchParams('bar=baz'))).toEqual('/foo?bar=baz');
   });
diff --git a/test/typescript/axios.ts b/test/typescript/axios.ts
index 94d41602c1..c0c61599e1 100644
--- a/test/typescript/axios.ts
+++ b/test/typescript/axios.ts
@@ -20,7 +20,10 @@ const config: AxiosRequestConfig = {
   ],
   headers: { 'X-FOO': 'bar' },
   params: { id: 12345 },
-  paramsSerializer: (params: any) => 'id=12345',
+  paramsSerializer: {
+    indexes: true,
+    encode: (value) => value
+  },
   data: { foo: 'bar' },
   timeout: 10000,
   withCredentials: true,