diff --git a/underscore/underscore.d.ts b/underscore/underscore.d.ts
index 23646f044..feca73688 100644
--- a/underscore/underscore.d.ts
+++ b/underscore/underscore.d.ts
@@ -961,6 +961,30 @@ interface UnderscoreStatic {
 		array: _.List<T>,
 		value: T,
 		from?: number): number;
+		
+	/**
+	 * Returns the first index of an element in `array` where the predicate truth test passes
+	 * @param array The array to search for the index of the first element where the predicate truth test passes.
+	 * @param predicate Predicate function.
+	 * @param context `this` object in `predicate`, optional.
+	 * @return Returns the index of an element in `array` where the predicate truth test passes or -1.`
+	 **/
+	findIndex<T>(
+		array: _.List<T>,
+		predicate: _.ListIterator<T, boolean>,
+		context?: any): number;
+		
+	/**
+	 * Returns the last index of an element in `array` where the predicate truth test passes
+	 * @param array The array to search for the index of the last element where the predicate truth test passes.
+	 * @param predicate Predicate function.
+	 * @param context `this` object in `predicate`, optional.
+	 * @return Returns the index of an element in `array` where the predicate truth test passes or -1.`
+	 **/
+	findLastIndex<T>(
+		array: _.List<T>,
+		predicate: _.ListIterator<T, boolean>,
+		context?: any): number;
 
 	/**
 	* Uses a binary search to determine the index at which the value should be inserted into the list in order
@@ -2115,6 +2139,16 @@ interface Underscore<T> {
 	**/
 	lastIndexOf(value: T, from?: number): number;
 
+	/**
+	 * @see _.findIndex
+	 **/
+	findIndex<T>(array: _.List<T>, predicate: _.ListIterator<T, boolean>, context?: any): number;
+
+	/**
+	 * @see _.findLastIndex
+	 **/
+	findLastIndex<T>(array: _.List<T>, predicate: _.ListIterator<T, boolean>, context?: any): number;
+
 	/**
 	* Wrapped type `any[]`.
 	* @see _.sortedIndex
@@ -2999,6 +3033,16 @@ interface _Chain<T> {
 	**/
 	lastIndexOf(value: T, from?: number): _ChainSingle<T>;
 
+	/**
+	 * @see _.findIndex
+	 **/
+	findIndex<T>(predicate: _.ListIterator<T, boolean>, context?: any): _Chain<T>;
+
+	/**
+	 * @see _.findLastIndex
+	 **/
+	findLastIndex<T>(predicate: _.ListIterator<T, boolean>, context?: any): _Chain<T>;
+
 	/**
 	* Wrapped type `any[]`.
 	* @see _.sortedIndex