diff --git a/README.md b/README.md
index 943a435..0f472d3 100644
--- a/README.md
+++ b/README.md
@@ -1,6 +1,6 @@
 # clone-deep [![NPM version](https://img.shields.io/npm/v/clone-deep.svg?style=flat)](https://www.npmjs.com/package/clone-deep) [![NPM monthly downloads](https://img.shields.io/npm/dm/clone-deep.svg?style=flat)](https://npmjs.org/package/clone-deep) [![NPM total downloads](https://img.shields.io/npm/dt/clone-deep.svg?style=flat)](https://npmjs.org/package/clone-deep) [![Linux Build Status](https://img.shields.io/travis/jonschlinkert/clone-deep.svg?style=flat&label=Travis)](https://travis-ci.org/jonschlinkert/clone-deep)
 
-> Recursively (deep) clone JavaScript native types, like Object, Array, RegExp, Date as well as primitives.
+> Recursively (deep) clone JavaScript native types, like Object, Array, RegExp, Date as well as primitives. Supports circular objects clonning.
 
 Please consider following this project's author, [Jon Schlinkert](https://github.com/jonschlinkert), and consider starring the project to show your :heart: and support.
 
@@ -19,6 +19,7 @@ const cloneDeep = require('clone-deep');
 
 let obj = { a: 'b' };
 let arr = [obj];
+
 let copy = cloneDeep(arr);
 obj.c = 'd';
 
@@ -27,6 +28,12 @@ console.log(copy);
 
 console.log(arr);
 //=> [{ a: 'b', c: 'd' }]
+
+obj.e = obj;
+copy = cloneDeep(arr);
+
+console.log(copy);
+//=> [{ a: 'b', c: 'd', e: {...} }] // handles circular arrays and objects cloning
 ```
 
 ## Heads up!
@@ -84,9 +91,10 @@ You might also be interested in these projects:
 ### Contributors
 
 | **Commits** | **Contributor** |  
-| --- | --- |  
+| -- | --- |  
 | 46 | [jonschlinkert](https://github.com/jonschlinkert) |  
-| 2  | [yujunlong2000](https://github.com/yujunlong2000) |  
+| 2 | [yujunlong2000](https://github.com/yujunlong2000) |  
+| 5  | [emahuni](https://github.com/emahuni) |  
 
 ### Author
 
diff --git a/index.js b/index.js
index 9133c08..cfb13fc 100644
--- a/index.js
+++ b/index.js
@@ -7,41 +7,96 @@
 const clone = require('shallow-clone');
 const typeOf = require('kind-of');
 const isPlainObject = require('is-plain-object');
+const findIndex = require('lodash.findindex');
+const isEqual = require('lodash.isequal');
 
-function cloneDeep(val, instanceClone) {
+
+function cloneDeep (val, instanceClone) {
+  // get an instance of the main val into parentsRes first, we need this for checking and setting of clone circular references
+  // undefined root will skip cloning in cloneObjectDeep and just get the new instance
+  const parentsRes = [_cloneDeep(val, instanceClone)];
+
+  // don't repeat if these will result same as parentsRes[0]
+  if (/array|object/.test(typeOf(val))) {
+    if (!/function|undefined/.test(typeof instanceClone) || typeof val === 'object') {
+      return _cloneDeep(val, instanceClone, parentsRes[0], parentsRes, [val]);
+    }
+  }
+  return parentsRes[0];
+}
+
+
+function _cloneDeep (val, instanceClone, root, parentsRes, parentsVal) {
   switch (typeOf(val)) {
-    case 'object':
-      return cloneObjectDeep(val, instanceClone);
     case 'array':
-      return cloneArrayDeep(val, instanceClone);
+    case 'object':
+      return cloneObjectDeep(val, instanceClone, root, parentsRes, parentsVal);
     default: {
       return clone(val);
     }
   }
 }
 
-function cloneObjectDeep(val, instanceClone) {
+
+function cloneObjectDeep (val, instanceClone, root, parentsRes, parentsVal) {
   if (typeof instanceClone === 'function') {
     return instanceClone(val);
   }
-  if (instanceClone || isPlainObject(val)) {
-    const res = new val.constructor();
-    for (let key in val) {
-      res[key] = cloneDeep(val[key], instanceClone);
+
+  if (instanceClone || isArrayOrPlainObject(val)) {
+    let res;
+    if (root) {
+      res = root; // don't directly use root to avoid confusion
+    } else {
+      res = new val.constructor(Array.isArray(val) ? val.length : undefined);
     }
+
+    // if root is undefined then this was just a clone object constructor
+    if (root) {
+      for (let key in val) {
+        const isValObj = isArrayOrObject(val[key]);
+
+        let circularIndex;
+        if (isValObj) circularIndex = findIndex(parentsVal, v => isEqual(v, val[key]));
+
+        if (circularIndex !== undefined && ~circularIndex) {
+          res[key] = parentsRes[circularIndex];
+        } else {
+          if (isValObj || (instanceClone && (typeof instanceClone === typeof val[key] || typeof val[key] === 'function'))) {
+            // this is some kind of object
+            parentsVal.push(val[key]);
+
+            const keyRoot = _cloneDeep(val[key], instanceClone); // get instance for object at val[key]
+            res[key] = keyRoot;
+            parentsRes.push(keyRoot);
+
+            // the following will clone val[key] object on keyRoot/res[key]
+            _cloneDeep(val[key], instanceClone, keyRoot, parentsRes, parentsVal);
+          } else {
+            // this is a scalar property
+            res[key] = _cloneDeep(val[key], instanceClone, res, parentsRes, parentsVal);
+          }
+        }
+      }
+    }
+
     return res;
   }
+
   return val;
 }
 
-function cloneArrayDeep(val, instanceClone) {
-  const res = new val.constructor(val.length);
-  for (let i = 0; i < val.length; i++) {
-    res[i] = cloneDeep(val[i], instanceClone);
-  }
-  return res;
+
+function isArrayOrPlainObject (val) {
+  return Array.isArray(val) || isPlainObject(val);
+}
+
+
+function isArrayOrObject (val) {
+  return Array.isArray(val) || typeOf(val) === 'object';
 }
 
+
 /**
  * Expose `cloneDeep`
  */
diff --git a/package.json b/package.json
index 7b494ea..b98eb03 100644
--- a/package.json
+++ b/package.json
@@ -22,6 +22,8 @@
   "dependencies": {
     "is-plain-object": "^2.0.4",
     "kind-of": "^6.0.2",
+    "lodash.findindex": "^4.6.0",
+    "lodash.isequal": "^4.5.0",
     "shallow-clone": "^3.0.0"
   },
   "devDependencies": {
diff --git a/test.js b/test.js
index a93725e..b301f92 100644
--- a/test.js
+++ b/test.js
@@ -4,8 +4,8 @@ require('mocha');
 const assert = require('assert');
 const clone = require('./');
 
-describe('cloneDeep()', function() {
-  it('should clone arrays', function() {
+describe('cloneDeep()', function () {
+  it('should clone arrays', function () {
     assert.deepEqual(clone(['alpha', 'beta', 'gamma']), ['alpha', 'beta', 'gamma']);
     assert.deepEqual(clone([1, 2, 3]), [1, 2, 3]);
 
@@ -15,12 +15,12 @@ describe('cloneDeep()', function() {
     assert.deepEqual(b, a);
     assert.deepEqual(b[0], a[0]);
 
-    const val = [0, 'a', {}, [{}], [function() {}], function() {}];
+    const val = [0, 'a', {}, [{}], [function () {}], function () {}];
     assert.deepEqual(clone(val), val);
   });
 
-  it('should deeply clone an array', function() {
-    const fixture = [[{a: 'b'}], [{a: 'b'}]];
+  it('should deeply clone an array', function () {
+    const fixture = [[{ a: 'b' }], [{ a: 'b' }]];
     const result = clone(fixture);
     assert(fixture !== result);
     assert(fixture[0] !== result[0]);
@@ -28,64 +28,101 @@ describe('cloneDeep()', function() {
     assert.deepEqual(fixture, result);
   });
 
-  it('should deeply clone object', function() {
-    const one = {a: 'b'};
+  it('should deeply clone object', function () {
+    const one = { a: 'b' };
     const two = clone(one);
     two.c = 'd';
     assert.notDeepEqual(one, two);
   });
 
-  it('should deeply clone arrays', function() {
-    const one = {a: 'b'};
+  it('should deeply clone arrays', function () {
+    const one = { a: 'b' };
     const arr1 = [one];
     const arr2 = clone(arr1);
     one.c = 'd';
     assert.notDeepEqual(arr1, arr2);
   });
 
-  it('should deeply clone Map', function() {
+  it('should deeply clone object with circular references if pointing to root object', function () {
+    const one = { a: false, b: { c: '3' } };
+    one.b.cyclic = one.b;
+    const two = clone(one);
+    two.b.cyclic.c = 'e';
+    assert.notDeepEqual(one, two);
+    assert.equal(two.b, two.b.cyclic);
+    assert.notEqual(one.b.cyclic.c, two.b.cyclic.c);
+  });
+
+  it('should deeply clone object with circular references if pointing to inner object', function () {
+    const one = { a: false, b: { c: '3' } };
+    one.b.cyclic = one;
+    const two = clone(one);
+    two.b.cyclic.a = true;
+    assert.notDeepEqual(one, two);
+    assert.equal(two, two.b.cyclic);
+    assert.notEqual(one.b.cyclic.a, two.b.cyclic.a);
+  });
+
+  it('should deeply clone arrays with circular references', function () {
+    const one = { a: 'b' };
+    const arr1 = [one];
+    arr1.push(arr1);
+    const arr2 = clone(arr1);
+    one.a = 'c';
+    assert.notDeepEqual(arr1, arr2);
+    assert.equal(arr2, arr2[1]);
+    assert.notEqual(arr1[1][0].a, arr2[1][0].a);
+  });
+
+  it('should deeply clone Map', function () {
     const a = new Map([[1, 5]]);
     const b = clone(a);
     a.set(2, 4);
     assert.notDeepEqual(Array.from(a), Array.from(b));
   });
 
-  it('should deeply clone Set', function() {
+  it('should deeply clone Set', function () {
     const a = new Set([2, 1, 3]);
     const b = clone(a);
     a.add(8);
     assert.notDeepEqual(Array.from(a), Array.from(b));
   });
 
-  it('should return primitives', function() {
+  it('should return primitives', function () {
     assert.equal(clone(0), 0);
     assert.equal(clone('foo'), 'foo');
   });
 
-  it('should clone a regex', function() {
+  it('should clone a regex', function () {
     assert.deepEqual(clone(/foo/g), /foo/g);
   });
 
-  it('should clone objects', function() {
-    assert.deepEqual(clone({a: 1, b: 2, c: 3 }), {a: 1, b: 2, c: 3 });
+  it('should clone objects', function () {
+    assert.deepEqual(clone({ a: 1, b: 2, c: 3 }), { a: 1, b: 2, c: 3 });
   });
 
-  it('should deeply clone objects', function() {
-    assert.deepEqual(clone({a: {a: 1, b: 2, c: 3 }, b: {a: 1, b: 2, c: 3 }, c: {a: 1, b: 2, c: 3 } }), {a: {a: 1, b: 2, c: 3 }, b: {a: 1, b: 2, c: 3 }, c: {a: 1, b: 2, c: 3 } });
+  it('should deeply clone objects', function () {
+    assert.deepEqual(clone({ a: { a: 1, b: 2, c: 3 }, b: { a: 1, b: 2, c: 3 }, c: { a: 1, b: 2, c: 3 } }), {
+      a: { a: 1, b: 2, c: 3 },
+      b: { a: 1, b: 2, c: 3 },
+      c: { a: 1, b: 2, c: 3 },
+    });
   });
 
-  it('should deep clone instances with instanceClone true', function() {
-    function A(x, y, z) {
+  it('should deep clone instances with instanceClone true', function () {
+    function A (x, y, z) {
       this.x = x;
       this.y = y;
       this.z = z;
     }
 
-    function B(x) {
+
+    function B (x) {
       this.x = x;
     }
 
-    const a = new A({x: 11, y: 12, z: () => 'z'}, new B(2), 7);
+
+    const a = new A({ x: 11, y: 12, z: () => 'z' }, new B(2), 7);
     const b = clone(a, true);
 
     assert.deepEqual(a, b);
@@ -97,18 +134,20 @@ describe('cloneDeep()', function() {
     assert.notEqual(a.y.x, b.y.x, 'Nested property of original object not expected to be changed');
   });
 
-  it('should not deep clone instances', function() {
-    function A(x, y, z) {
+  it('should not deep clone instances', function () {
+    function A (x, y, z) {
       this.x = x;
       this.y = y;
       this.z = z;
     }
 
-    function B(x) {
+
+    function B (x) {
       this.x = x;
     }
 
-    const a = new A({x: 11, y: 12, z: () => 'z'}, new B(2), 7);
+
+    const a = new A({ x: 11, y: 12, z: () => 'z' }, new B(2), 7);
     const b = clone(a);
 
     assert.deepEqual(a, b);
@@ -120,19 +159,21 @@ describe('cloneDeep()', function() {
     assert.equal(a.y.x, b.y.x);
   });
 
-  it('should deep clone instances with instanceClone self defined', function() {
-    function A(x, y, z) {
+  it('should deep clone instances with instanceClone self defined', function () {
+    function A (x, y, z) {
       this.x = x;
       this.y = y;
       this.z = z;
     }
 
-    function B(x) {
+
+    function B (x) {
       this.x = x;
     }
 
-    const a = new A({x: 11, y: 12, z: () => 'z'}, new B(2), 7);
-    const b = clone(a, function(val){
+
+    const a = new A({ x: 11, y: 12, z: () => 'z' }, new B(2), 7);
+    const b = clone(a, function (val) {
       if (val instanceof A) {
         const res = new A();
         for (const key in val) {