diff --git a/lodash/lodash-tests.ts b/lodash/lodash-tests.ts
index c56d79817..e7e827300 100644
--- a/lodash/lodash-tests.ts
+++ b/lodash/lodash-tests.ts
@@ -261,12 +261,41 @@ result = <_.List<string>>_.fill<string>(testFillList, 'a', 0, 3);
 result = <number[]>_(testFillArray).fill<number>(0, 0, 3).value();
 result = <_.List<number>>_(testFillList).fill<number>(0, 0, 3).value();
 
+// _.findIndex
+module TestFindIndex {
+    let array: TResult[];
+    let list: _.List<TResult>;
+    let predicateFn: (value: TResult, index?: number, collection?: _.List<TResult>) => boolean;
+    let result: number;
 
-result = <number>_.findIndex(['apple', 'banana', 'beet'], function (f) {
-    return /^b/.test(f);
-});
-result = <number>_.findIndex(['apple', 'banana', 'beet'], 'apple');
-result = <number>_.findIndex([{ food: 'apple' }, { food: 'banana' }, { food: 'beet' }], { food: 'apple' });
+    result = _.findIndex<TResult>(array);
+    result = _.findIndex<TResult>(array, predicateFn);
+    result = _.findIndex<TResult>(array, predicateFn, any);
+    result = _.findIndex<TResult>(array, '');
+    result = _.findIndex<TResult>(array, '', any);
+    result = _.findIndex<{a: number}, TResult>(array, {a: 42});
+
+    result = _.findIndex<TResult>(list);
+    result = _.findIndex<TResult>(list, predicateFn);
+    result = _.findIndex<TResult>(list, predicateFn, any);
+    result = _.findIndex<TResult>(list, '');
+    result = _.findIndex<TResult>(list, '', any);
+    result = _.findIndex<{a: number}, TResult>(list, {a: 42});
+
+    result = _<TResult>(array).findIndex();
+    result = _<TResult>(array).findIndex(predicateFn);
+    result = _<TResult>(array).findIndex(predicateFn, any);
+    result = _<TResult>(array).findIndex('');
+    result = _<TResult>(array).findIndex('', any);
+    result = _<TResult>(array).findIndex<{a: number}>({a: 42});
+
+    result = _(list).findIndex();
+    result = _(list).findIndex<TResult>(predicateFn);
+    result = _(list).findIndex<TResult>(predicateFn, any);
+    result = _(list).findIndex('');
+    result = _(list).findIndex('', any);
+    result = _(list).findIndex<{a: number}>({a: 42});
+}
 
 result = <number>_.findLastIndex(['apple', 'banana', 'beet'], function (f: string) {
     return /^b/.test(f);
diff --git a/lodash/lodash.d.ts b/lodash/lodash.d.ts
index 5d8afa549..10171fd57 100644
--- a/lodash/lodash.d.ts
+++ b/lodash/lodash.d.ts
@@ -460,54 +460,95 @@ declare module _ {
     //_.findIndex
     interface LoDashStatic {
         /**
-        * This method is like _.find except that it returns the index of the first element that passes
-        * the callback check, instead of the element itself.
-        * @param array The array to search.
-        * @param {(Function|Object|string)} callback The function called per iteration. If a property name or object is provided it will be
-        * used to create a ".pluck" or ".where" style callback, respectively.
-        * @param thisArg The this binding of callback.
-        * @return Returns the index of the found element, else -1.
-        **/
-        findIndex<T>(
-            array: Array<T>,
-            callback: ListIterator<T, boolean>,
-            thisArg?: any): number;
-
-        /**
-        * @see _.findIndex
-        **/
+         * This method is like _.find except that it returns the index of the first element predicate returns truthy
+         * for instead of the element itself.
+         *
+         * If a property name is provided for predicate the created _.property style callback returns the property
+         * value of the given element.
+         *
+         * If a value is also provided for thisArg the created _.matchesProperty style callback returns true for
+         * elements that have a matching property value, else false.
+         *
+         * If an object is provided for predicate the created _.matches style callback returns true for elements that
+         * have the properties of the given object, else false.
+         *
+         * @param array The array to search.
+         * @param predicate The function invoked per iteration.
+         * @param thisArg The this binding of predicate.
+         * @return Returns the index of the found element, else -1.
+         */
         findIndex<T>(
             array: List<T>,
-            callback: ListIterator<T, boolean>,
-            thisArg?: any): number;
+            predicate?: ListIterator<T, boolean>,
+            thisArg?: any
+        ): number;
 
         /**
-        * @see _.findIndex
-        **/
-        findIndex<T>(
-            array: Array<T>,
-            pluckValue: string): number;
-
-        /**
-        * @see _.findIndex
-        **/
+         * @see _.findIndex
+         */
         findIndex<T>(
             array: List<T>,
-            pluckValue: string): number;
+            predicate?: string,
+            thisArg?: any
+        ): number;
 
         /**
-        * @see _.findIndex
-        **/
-        findIndex<W, T>(
-            array: Array<T>,
-            whereDictionary: W): number;
-
-        /**
-        * @see _.findIndex
-        **/
+         * @see _.findIndex
+         */
         findIndex<W, T>(
             array: List<T>,
-            whereDictionary: W): number;
+            predicate?: W
+        ): number;
+    }
+
+    interface LoDashArrayWrapper<T> {
+        /**
+         * @see _.findIndex
+         */
+        findIndex(
+            predicate?: ListIterator<T, boolean>,
+            thisArg?: any
+        ): number;
+
+        /**
+         * @see _.findIndex
+         */
+        findIndex(
+            predicate?: string,
+            thisArg?: any
+        ): number;
+
+        /**
+         * @see _.findIndex
+         */
+        findIndex<W>(
+            predicate?: W
+        ): number;
+    }
+
+    interface LoDashObjectWrapper<T> {
+        /**
+         * @see _.findIndex
+         */
+        findIndex<TResult>(
+            predicate?: ListIterator<TResult, boolean>,
+            thisArg?: any
+        ): number;
+
+        /**
+         * @see _.findIndex
+         */
+        findIndex(
+            predicate?: string,
+            thisArg?: any
+        ): number;
+
+        /**
+         * @see _.findIndex
+         */
+        findIndex<W>(
+            predicate?: W
+        ): number;
     }
 
     //_.findLastIndex