diff --git a/src/Helpers.php b/src/Helpers.php
index 182c60d..19eacd5 100644
--- a/src/Helpers.php
+++ b/src/Helpers.php
@@ -34,5 +34,8 @@ class Helpers extends BaseHelpers
         $this->add('ifEven', new Comparison\IfEvenHelper());
         $this->add('ifOdd', new Comparison\IfOddHelper());
         $this->add('unlessEqual', new Comparison\UnlessEqualHelper());
+
+        // String helpers
+        $this->add('lowercase', new String\LowercaseHelper());
     }
 }
diff --git a/src/String/Helpers.php b/src/String/Helpers.php
new file mode 100644
index 0000000..1f75baa
--- /dev/null
+++ b/src/String/Helpers.php
@@ -0,0 +1,31 @@
+<?php
+/*
+ * This file is part of Handlebars.php Helpers Set
+ *
+ * (c) Dmitriy Simushev <simushevds@gmail.com>
+ *
+ * For the full copyright and license information, please view the LICENSE
+ * file that was distributed with this source code.
+ */
+
+namespace JustBlackBird\HandlebarsHelpers\String;
+
+use Handlebars\Helpers as BaseHelpers;
+
+/**
+ * Contains all strings related helpers.
+ *
+ * @author Dmitriy Simushev <simushevds@gmail.com>
+ */
+class Helpers extends BaseHelpers
+{
+    /**
+     * {@inheritdoc}
+     */
+    protected function addDefaultHelpers()
+    {
+        parent::addDefaultHelpers();
+
+        $this->add('lowercase', new LowercaseHelper());
+    }
+}
diff --git a/src/String/LowercaseHelper.php b/src/String/LowercaseHelper.php
new file mode 100644
index 0000000..56e8dcc
--- /dev/null
+++ b/src/String/LowercaseHelper.php
@@ -0,0 +1,46 @@
+<?php
+/*
+ * This file is part of Handlebars.php Helpers Set
+ *
+ * (c) Dmitriy Simushev <simushevds@gmail.com>
+ *
+ * For the full copyright and license information, please view the LICENSE
+ * file that was distributed with this source code.
+ */
+
+namespace JustBlackBird\HandlebarsHelpers\String;
+
+use Handlebars\Context;
+use Handlebars\Helper as HelperInterface;
+use Handlebars\Template;
+
+/**
+ * Converts a string to lowercase.
+ *
+ * Usage:
+ * ```handlebars
+ *   {{lowercase string}}
+ * ```
+ *
+ * Arguments:
+ *  - "string": A string that should be converted to lowercase.
+ *
+ * @author Dmitriy Simushev <simushevds@gmail.com>
+ */
+class LowercaseHelper implements HelperInterface
+{
+    /**
+     * {@inheritdoc}
+     */
+    public function execute(Template $template, Context $context, $args, $source)
+    {
+        $parsed_args = $template->parseArguments($args);
+        if (count($parsed_args) != 1) {
+            throw new \InvalidArgumentException(
+                '"lowercase" helper expects exactly one argument.'
+            );
+        }
+
+        return strtolower($context->get($parsed_args[0]));
+    }
+}
diff --git a/tests/HelpersTest.php b/tests/HelpersTest.php
index bedcfaa..f47e8ee 100644
--- a/tests/HelpersTest.php
+++ b/tests/HelpersTest.php
@@ -46,6 +46,9 @@ class HelpersTest extends \PHPUnit_Framework_TestCase
             array('ifEven', '\\JustBlackBird\\HandlebarsHelpers\\Comparison\\IfEvenHelper'),
             array('ifOdd', '\\JustBlackBird\\HandlebarsHelpers\\Comparison\\IfOddHelper'),
             array('unlessEqual', '\\JustBlackBird\\HandlebarsHelpers\\Comparison\\UnlessEqualHelper'),
+
+            // String helpers
+            array('lowercase', '\\JustBlackBird\\HandlebarsHelpers\\String\\LowercaseHelper'),
         );
     }
 }
diff --git a/tests/String/HelpersTest.php b/tests/String/HelpersTest.php
new file mode 100644
index 0000000..b649c3e
--- /dev/null
+++ b/tests/String/HelpersTest.php
@@ -0,0 +1,44 @@
+<?php
+/*
+ * This file is part of Handlebars.php Helpers Set
+ *
+ * (c) Dmitriy Simushev <simushevds@gmail.com>
+ *
+ * For the full copyright and license information, please view the LICENSE
+ * file that was distributed with this source code.
+ */
+
+namespace JustBlackBird\HandlebarsHelpers\Tests\String;
+
+use JustBlackBird\HandlebarsHelpers\String\Helpers;
+
+/**
+ * Test class for String Helpers Set.
+ *
+ * @author Dmitriy Simushev <simushevds@gmail.com>
+ */
+class HelpersTest extends \PHPUnit_Framework_TestCase
+{
+    /**
+     * Tests that all helpers in the set exist and have valid classes.
+     *
+     * @dataProvider helpersProvider
+     */
+    public function testHelper($name, $class)
+    {
+        $helpers = new Helpers();
+
+        $this->assertTrue($helpers->has($name), sprintf('There is no "%s" helper', $name));
+        $this->assertInstanceOf($class, $helpers->{$name});
+    }
+
+    /**
+     * A data provider for testHelper method.
+     */
+    public function helpersProvider()
+    {
+        return array(
+            array('lowercase', '\\JustBlackBird\\HandlebarsHelpers\\String\\LowercaseHelper'),
+        );
+    }
+}
diff --git a/tests/String/LowercaseHelperTest.php b/tests/String/LowercaseHelperTest.php
new file mode 100644
index 0000000..e9734d8
--- /dev/null
+++ b/tests/String/LowercaseHelperTest.php
@@ -0,0 +1,80 @@
+<?php
+/*
+ * This file is part of Handlebars.php Helpers Set
+ *
+ * (c) Dmitriy Simushev <simushevds@gmail.com>
+ *
+ * For the full copyright and license information, please view the LICENSE
+ * file that was distributed with this source code.
+ */
+
+namespace JustBlackBird\HandlebarsHelpers\Tests\String;
+
+use JustBlackBird\HandlebarsHelpers\String\LowercaseHelper;
+
+/**
+ * Test class for "lowercase" helper.
+ *
+ * @author Dmitriy Simushev <simushevds@gmail.com>
+ */
+class LowercaseHelperTest extends \PHPUnit_Framework_TestCase
+{
+    /**
+     * Tests that strings are converted to lowercase properly.
+     *
+     * @dataProvider convertProvider
+     */
+    public function testConvert($string)
+    {
+        $helpers = new \Handlebars\Helpers(array('lowercase' => new LowercaseHelper()));
+        $engine = new \Handlebars\Handlebars(array('helpers' => $helpers));
+
+        $this->assertEquals(
+            $engine->render(
+                '{{lowercase str}}',
+                array('str' => $string)
+            ),
+            strtolower($string)
+        );
+    }
+
+    /**
+     * A data provider for testConvert method.
+     */
+    public function convertProvider()
+    {
+        return array(
+            array('already in lower'),
+            array('Mixed Case String'),
+            array('ANOther mIxed CASE string'),
+            array('STRING IN CAPS'),
+        );
+    }
+
+    /**
+     * Tests that exception is thrown if wrong number of arguments is used.
+     *
+     * @expectedException InvalidArgumentException
+     * @dataProvider wrongArgumentsProvider
+     */
+    public function testArgumentsCount($template)
+    {
+        $helpers = new \Handlebars\Helpers(array('lowercase' => new LowercaseHelper()));
+        $engine = new \Handlebars\Handlebars(array('helpers' => $helpers));
+
+        $engine->render($template, array());
+    }
+
+    /**
+     * A data provider for testArgumentsCount method.
+     */
+    public function wrongArgumentsProvider()
+    {
+        return array(
+            // Not enough arguments
+            array('{{lowercase}}'),
+            // Too much arguments
+            array('{{lowercase "Arg" "ANOTHER ARG"}}'),
+        );
+    }
+}