diff --git a/src/Message/Header/HeaderCollection.php b/src/Message/Header/HeaderCollection.php
new file mode 100644
index 0000000..045b28a
--- /dev/null
+++ b/src/Message/Header/HeaderCollection.php
@@ -0,0 +1,39 @@
+<?php
+
+namespace WellRESTed\Message\Header;
+
+class HeaderCollection implements \ArrayAccess
+{
+    private $headers;
+
+    public function __construct()
+    {
+        $this->headers = [];
+    }
+
+    public function offsetExists($offset)
+    {
+        return isset($this->headers[strtolower($offset)]);
+    }
+
+    public function offsetGet($offset)
+    {
+        return $this->headers[strtolower($offset)];
+    }
+
+    public function offsetSet($offset, $value)
+    {
+        $header = new Header($offset, $value);
+        $normalized = strtolower($offset);
+        if (isset($this->headers[$normalized])) {
+            $this->headers[$normalized][] = $header;
+        } else {
+            $this->headers[$normalized] = [$header];
+        }
+    }
+
+    public function offsetUnset($offset)
+    {
+        unset($this->headers[strtolower($offset)]);
+    }
+}
diff --git a/test/tests/unit/Message/Header/HeaderCollectionTest.php b/test/tests/unit/Message/Header/HeaderCollectionTest.php
new file mode 100644
index 0000000..3b14178
--- /dev/null
+++ b/test/tests/unit/Message/Header/HeaderCollectionTest.php
@@ -0,0 +1,77 @@
+<?php
+
+namespace pjdietz\WellRESTed\Test\Message\Header;
+
+use WellRESTed\Message\Header\HeaderCollection;
+
+class HeaderCollectionTest extends \PHPUnit_Framework_TestCase
+{
+    /**
+     * @covers WellRESTed\Message\Header\HeaderCollection::__construct
+     */
+    public function testCreatesInstance()
+    {
+        $collection = new HeaderCollection();
+        $this->assertNotNull($collection);
+    }
+
+    /**
+     * @covers WellRESTed\Message\Header\HeaderCollection::offsetSet
+     * @covers WellRESTed\Message\Header\HeaderCollection::offsetExists
+     * @uses WellRESTed\Message\Header\HeaderCollection::__construct
+     * @uses WellRESTed\Message\Header\Header
+     */
+    public function testAddsSingleHeaderAndIndicatesCaseInsensitiveIsset()
+    {
+        $collection = new HeaderCollection();
+        $collection["Content-Type"] = "application/json";
+        $this->assertTrue(isset($collection["content-type"]));
+    }
+
+    /**
+     * @covers WellRESTed\Message\Header\HeaderCollection::offsetSet
+     * @covers WellRESTed\Message\Header\HeaderCollection::offsetExists
+     * @uses WellRESTed\Message\Header\HeaderCollection::__construct
+     * @uses WellRESTed\Message\Header\Header
+     */
+    public function testAddsMultipleHeadersAndIndicatesCaseInsensitiveIsset()
+    {
+        $collection = new HeaderCollection();
+        $collection["Set-Cookie"] = "cat=Molly";
+        $collection["SET-COOKIE"] = "dog=Bear";
+        $this->assertTrue(isset($collection["set-cookie"]));
+    }
+
+    /**
+     * @covers WellRESTed\Message\Header\HeaderCollection::offsetGet
+     * @uses WellRESTed\Message\Header\HeaderCollection::offsetSet
+     * @uses WellRESTed\Message\Header\HeaderCollection::__construct
+     * @uses WellRESTed\Message\Header\Header
+     */
+    public function testReturnsHeadersWithCaseInsensitiveHeaderName()
+    {
+        $collection = new HeaderCollection();
+        $collection["Set-Cookie"] = "cat=Molly";
+        $collection["SET-COOKIE"] = "dog=Bear";
+
+        $headers = $collection["set-cookie"];
+        $this->assertContains("Set-Cookie: cat=Molly", $headers);
+        $this->assertContains("SET-COOKIE: dog=Bear", $headers);
+    }
+
+    /**
+     * @covers WellRESTed\Message\Header\HeaderCollection::offsetUnset
+     * @uses WellRESTed\Message\Header\HeaderCollection::__construct
+     * @uses WellRESTed\Message\Header\HeaderCollection::offsetSet
+     * @uses WellRESTed\Message\Header\HeaderCollection::offsetExists
+     * @uses WellRESTed\Message\Header\Header
+     */
+    public function testRemovesHeadersWithCaseInsensitiveHeaderName()
+    {
+        $collection = new HeaderCollection();
+        $collection["Set-Cookie"] = "cat=Molly";
+        $collection["SET-COOKIE"] = "dog=Bear";
+        unset($collection["set-cookie"]);
+        $this->assertFalse(isset($collection["set-cookie"]));
+    }
+}