diff --git a/CHANGELOG.md b/CHANGELOG.md
index 773df51..2d7090a 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -5,6 +5,10 @@ All notable changes to this project will be documented in this file.
 The format is based on [Keep a Changelog](https://keepachangelog.com/en/1.0.0/),
 and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0.html).
 
+## [1.1.0] - 2025-04-12
+### Added
+- Add optional `key` argument to `AbstractCollection::add()` method
+
 ## [1.0.2] - 2025-04-10
 ### Changed
 - Increased unit test coverage to 100%
diff --git a/README.md b/README.md
index b294f7c..0d60541 100644
--- a/README.md
+++ b/README.md
@@ -2,7 +2,7 @@
 
 <div>
 <!-- Version Badge -->
-<img src="https://img.shields.io/badge/Version-1.0.2-blue" alt="Version 1.0.2">
+<img src="https://img.shields.io/badge/Version-1.1.0-blue" alt="Version 1.1.0">
 <!-- PHP Coverage Badge -->
 <img src="https://img.shields.io/badge/PHP%20Coverage-100.00%25-green" alt="PHP Coverage 100.00%">
 <!-- License Badge -->
diff --git a/composer.json b/composer.json
index 70bacd0..4d90cc8 100644
--- a/composer.json
+++ b/composer.json
@@ -14,7 +14,7 @@
     "scripts": {
         "test": "php -d xdebug.mode=coverage ./vendor/bin/phpunit --testdox --colors=always --coverage-html coverage --coverage-clover coverage/coverage.xml --testdox-html coverage/testdox.html && npx badger --phpunit ./coverage/coverage.xml && npx badger --version ./composer.json && npx badger --license ./composer.json"
     },
-    "version": "1.0.2",
+    "version": "1.1.0",
     "license": "MIT",
     "require-dev": {
         "phpunit/phpunit": "^12.1"
diff --git a/src/AbstractCollection.php b/src/AbstractCollection.php
index fe12ddb..482c002 100644
--- a/src/AbstractCollection.php
+++ b/src/AbstractCollection.php
@@ -12,12 +12,18 @@ class AbstractCollection implements CollectionInterface
     {
     }
 
-    public function add(mixed $item): void
+    public function add(mixed $item, string $key = null): void
     {
         if (null === $item) {
             return;
         }
 
+        if ($key) {
+            $this->items[$key] = $item;
+
+            return;
+        }
+
         $this->items[] = $item;
     }
 
diff --git a/tests/CollectionTest.php b/tests/CollectionTest.php
index d740e71..d06c85f 100644
--- a/tests/CollectionTest.php
+++ b/tests/CollectionTest.php
@@ -11,10 +11,10 @@ use PHPUnit\Framework\TestCase;
 class CollectionTest extends TestCase
 {
     #[DataProvider('addDataProvider')]
-    public function testAdd(array $startingItems, mixed $itemToAdd, array $expectedResult): void
+    public function testAdd(array $startingItems, mixed $itemToAdd, array $expectedResult, string $key = null): void
     {
         $collection = new Collection($startingItems);
-        $collection->add($itemToAdd);
+        $collection->add($itemToAdd, $key);
 
         $this->assertEquals($expectedResult, $collection->toArray());
     }
@@ -52,17 +52,26 @@ class CollectionTest extends TestCase
                 'startingItems' => ['A', 'B', 'C'],
                 'itemToAdd' => 'D',
                 'expectedResult' => ['A', 'B', 'C', 'D'],
+                'key' => null,
             ],
             [
                 'startingItems' => [],
                 'itemToAdd' => 1,
                 'expectedResult' => [1],
+                'key' => null,
             ],
             [
                 'startingItems' => [],
                 'itemToAdd' => null,
                 'expectedResult' => [],
+                'key' => null,
             ],
+            [
+                'startingItems' => ['A' => 'A', 'B' => 'B', 'C' => 'C'],
+                'itemToAdd' => 'D',
+                'expectedResult' => ['A' => 'A', 'B' => 'B', 'C' => 'C', 'D' => 'D'],
+                'key' => 'D',
+            ]
         ];
     }