diff --git a/README.md b/README.md
index df1d3bf..c5a9029 100644
--- a/README.md
+++ b/README.md
@@ -217,6 +217,7 @@ 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 URLSearchParams object
   params: {
     ID: 12345
   },
@@ -229,7 +230,10 @@ 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', and 'PATCH'
-  // When no `transformRequest` is set, must be a string, an ArrayBuffer, a hash, or a Stream
+  // When no `transformRequest` is set, must be of one of the following types:
+  // - string, plain object, ArrayBuffer, ArrayBufferView, URLSearchParams
+  // - Browser only: FormData, File, Blob
+  // - Node only: Stream
   data: {
     firstName: 'Fred'
   },
diff --git a/lib/defaults.js b/lib/defaults.js
index 1942ce0..162ffa7 100644
--- a/lib/defaults.js
+++ b/lib/defaults.js
@@ -1,33 +1,39 @@
 'use strict';
 
 var utils = require('./utils');
+var normalizeHeaderName = require('./helpers/normalizeHeaderName');
 
 var PROTECTION_PREFIX = /^\)\]\}',?\n/;
 var DEFAULT_CONTENT_TYPE = {
   'Content-Type': 'application/x-www-form-urlencoded'
 };
 
+function setContentTypeIfUnset(headers, value) {
+  if (!utils.isUndefined(headers) && utils.isUndefined(headers['Content-Type'])) {
+    headers['Content-Type'] = value;
+  }
+}
+
 module.exports = {
   transformRequest: [function transformRequest(data, headers) {
-    if (utils.isFormData(data) || utils.isArrayBuffer(data) || utils.isStream(data)) {
+    normalizeHeaderName(headers, 'Content-Type');
+    if (utils.isFormData(data) ||
+      utils.isArrayBuffer(data) ||
+      utils.isStream(data) ||
+      utils.isFile(data) ||
+      utils.isBlob(data)
+    ) {
       return data;
     }
     if (utils.isArrayBufferView(data)) {
       return data.buffer;
     }
-    if (utils.isObject(data) && !utils.isFile(data) && !utils.isBlob(data)) {
-      // Set application/json if no Content-Type has been specified
-      if (!utils.isUndefined(headers)) {
-        utils.forEach(headers, function processContentTypeHeader(val, key) {
-          if (key.toLowerCase() === 'content-type') {
-            headers['Content-Type'] = val;
-          }
-        });
-
-        if (utils.isUndefined(headers['Content-Type'])) {
-          headers['Content-Type'] = 'application/json;charset=utf-8';
-        }
-      }
+    if (utils.isURLSearchParams(data)) {
+      setContentTypeIfUnset(headers, 'application/x-www-form-urlencoded;charset=utf-8');
+      return data.toString();
+    }
+    if (utils.isObject(data)) {
+      setContentTypeIfUnset(headers, 'application/json;charset=utf-8');
       return JSON.stringify(data);
     }
     return data;
diff --git a/lib/helpers/buildURL.js b/lib/helpers/buildURL.js
index c8365f4..1e66456 100644
--- a/lib/helpers/buildURL.js
+++ b/lib/helpers/buildURL.js
@@ -29,6 +29,8 @@ module.exports = function buildURL(url, params, paramsSerializer) {
   var serializedParams;
   if (paramsSerializer) {
     serializedParams = paramsSerializer(params);
+  } else if (utils.isURLSearchParams(params)) {
+    serializedParams = params.toString();
   } else {
     var parts = [];
 
@@ -64,4 +66,3 @@ module.exports = function buildURL(url, params, paramsSerializer) {
 
   return url;
 };
-
diff --git a/lib/helpers/normalizeHeaderName.js b/lib/helpers/normalizeHeaderName.js
new file mode 100644
index 0000000..738c9fe
--- /dev/null
+++ b/lib/helpers/normalizeHeaderName.js
@@ -0,0 +1,12 @@
+'use strict';
+
+var utils = require('../utils');
+
+module.exports = function normalizeHeaderName(headers, normalizedName) {
+  utils.forEach(headers, function processHeader(value, name) {
+    if (name !== normalizedName && name.toUpperCase() === normalizedName.toUpperCase()) {
+      headers[normalizedName] = value;
+      delete headers[name];
+    }
+  });
+};
diff --git a/lib/utils.js b/lib/utils.js
index b0d376b..74668df 100644
--- a/lib/utils.js
+++ b/lib/utils.js
@@ -142,6 +142,16 @@ function isStream(val) {
   return isObject(val) && isFunction(val.pipe);
 }
 
+/**
+ * Determine if a value is a URLSearchParams object
+ *
+ * @param {Object} val The value to test
+ * @returns {boolean} True if value is a URLSearchParams object, otherwise false
+ */
+function isURLSearchParams(val) {
+  return typeof URLSearchParams !== 'undefined' && val instanceof URLSearchParams;
+}
+
 /**
  * Trim excess whitespace off the beginning and end of a string
  *
@@ -259,6 +269,7 @@ module.exports = {
   isBlob: isBlob,
   isFunction: isFunction,
   isStream: isStream,
+  isURLSearchParams: isURLSearchParams,
   isStandardBrowserEnv: isStandardBrowserEnv,
   forEach: forEach,
   merge: merge,
diff --git a/package.json b/package.json
index 50befbf..6bfd96d 100644
--- a/package.json
+++ b/package.json
@@ -63,7 +63,8 @@
     "phantomjs-prebuilt": "2.1.6",
     "sinon": "1.17.3",
     "webpack": "1.12.14",
-    "webpack-dev-server": "1.14.1"
+    "webpack-dev-server": "1.14.1",
+    "url-search-params": "0.5.0"
   },
   "browser": {
     "./lib/adapters/http.js": "./lib/adapters/xhr.js"
diff --git a/test/specs/__helpers.js b/test/specs/__helpers.js
index 80ecc74..8a06d0d 100644
--- a/test/specs/__helpers.js
+++ b/test/specs/__helpers.js
@@ -1,6 +1,9 @@
 // Polyfill ES6 Promise
 require('es6-promise').polyfill();
 
+// Polyfill URLSearchParams
+URLSearchParams = require('url-search-params');
+
 // Import axios
 axios = require('../../index');
 
diff --git a/test/specs/helpers/buildURL.spec.js b/test/specs/helpers/buildURL.spec.js
index 453c1f9..83d7ba1 100644
--- a/test/specs/helpers/buildURL.spec.js
+++ b/test/specs/helpers/buildURL.spec.js
@@ -1,4 +1,5 @@
 var buildURL = require('../../../lib/helpers/buildURL');
+var URLSearchParams = require('url-search-params');
 
 describe('helpers::buildURL', function () {
   it('should support null params', function () {
@@ -60,7 +61,9 @@ describe('helpers::buildURL', function () {
     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/specs/helpers/normalizeHeaderName.spec.js b/test/specs/helpers/normalizeHeaderName.spec.js
new file mode 100644
index 0000000..d8d5e82
--- /dev/null
+++ b/test/specs/helpers/normalizeHeaderName.spec.js
@@ -0,0 +1,21 @@
+var normalizeHeaderName = require('../../../lib/helpers/normalizeHeaderName');
+
+describe('helpers::normalizeHeaderName', function () {
+  it('should normalize matching header name', function () {
+    var headers = {
+      'conTenT-Type': 'foo/bar',
+    };
+    normalizeHeaderName(headers, 'Content-Type');
+    expect(headers['Content-Type']).toBe('foo/bar');
+    expect(headers['conTenT-Type']).toBeUndefined();
+  });
+
+  it('should not change non-matching header name', function () {
+    var headers = {
+      'content-type': 'foo/bar',
+    };
+    normalizeHeaderName(headers, 'Content-Length');
+    expect(headers['content-type']).toBe('foo/bar');
+    expect(headers['Content-Length']).toBeUndefined();
+  });
+});
diff --git a/test/specs/requests.spec.js b/test/specs/requests.spec.js
index 053de1e..47be0b0 100644
--- a/test/specs/requests.spec.js
+++ b/test/specs/requests.spec.js
@@ -277,4 +277,17 @@ describe('requests', function () {
     });
   });
 
+  it('should support URLSearchParams', function (done) {
+    var params = new URLSearchParams();
+    params.append('param1', 'value1');
+    params.append('param2', 'value2');
+
+    axios.post('/foo', params);
+
+    getAjaxRequest().then(function (request) {
+      expect(request.requestHeaders['Content-Type']).toBe('application/x-www-form-urlencoded;charset=utf-8');
+      expect(request.params).toBe('param1=value1&param2=value2');
+      done();
+    });
+  });
 });
diff --git a/test/specs/utils/isX.spec.js b/test/specs/utils/isX.spec.js
index d58d113..7620f8c 100644
--- a/test/specs/utils/isX.spec.js
+++ b/test/specs/utils/isX.spec.js
@@ -78,4 +78,9 @@ describe('utils::isX', function () {
     expect(utils.isStream(new Stream.Readable())).toEqual(true);
     expect(utils.isStream({ foo: 'bar' })).toEqual(false);
   });
+
+  it('should validate URLSearchParams', function () {
+    expect(utils.isURLSearchParams(new URLSearchParams())).toEqual(true);
+    expect(utils.isURLSearchParams('foo=1&bar=2')).toEqual(false);
+  });
 });