diff --git a/fixtures/signature_help/calls.php b/fixtures/signature_help/calls.php
new file mode 100644
index 0000000..2dfc7f2
--- /dev/null
+++ b/fixtures/signature_help/calls.php
@@ -0,0 +1,55 @@
+<?php
+
+namespace Foo;
+
+class Test
+{
+    /**
+     * Constructor comment goes here
+     *
+     * @param string $first  First param
+     * @param int    $second Second param
+     * @param Test   $third  Third param with a longer description
+     */
+    public function __construct(string $first, int $second, Test $third)
+    {
+    }
+
+    /**
+     * Function doc
+     *
+     * @param SomethingElse $a A param with a different doc type
+     * @param int|null      $b Param with default value
+     */
+    public function foo(\DateTime $a, int $b = null)
+    {
+    }
+
+    public static function bar($a)
+    {
+    }
+
+    /**
+     * Method with no params
+     */
+    public function baz()
+    {
+    }
+}
+
+/**
+ * @param int  $i Global function param one
+ * @param bool $b Default false param
+ */
+function foo(int $i, bool $b = false)
+{
+}
+
+$t = new Test();
+$t->foo();
+$t->foo(1, );
+$t->baz();
+
+foo();
+
+Test::bar();
diff --git a/src/SignatureHelpProvider.php b/src/SignatureHelpProvider.php
index 862c0da..1b80b34 100644
--- a/src/SignatureHelpProvider.php
+++ b/src/SignatureHelpProvider.php
@@ -108,8 +108,10 @@ class SignatureHelpProvider
         $signatureInformation = new SignatureInformation();
         $signatureInformation->label = $label;
         $signatureInformation->parameters = $params;
+        $signatureInformation->documentation = $this->definitionResolver->getDocumentationFromNode($node);
         $signatureHelp = new SignatureHelp();
         $signatureHelp->signatures = [$signatureInformation];
+        $signatureHelp->activeSignature = 0;
         $signatureHelp->activeParameter = $activeParam;
         return $signatureHelp;
     }
diff --git a/tests/Server/TextDocument/SignatureHelpTest.php b/tests/Server/TextDocument/SignatureHelpTest.php
new file mode 100644
index 0000000..33a36d7
--- /dev/null
+++ b/tests/Server/TextDocument/SignatureHelpTest.php
@@ -0,0 +1,191 @@
+<?php
+declare(strict_types = 1);
+
+namespace LanguageServer\Tests\Server\TextDocument;
+
+use PHPUnit\Framework\TestCase;
+use LanguageServer\Tests\MockProtocolStream;
+use LanguageServer\{
+    Server, LanguageClient, PhpDocumentLoader, DefinitionResolver
+};
+use LanguageServer\Index\{Index, ProjectIndex, DependenciesIndex};
+use LanguageServer\ContentRetriever\FileSystemContentRetriever;
+use LanguageServer\Protocol\{
+    TextDocumentIdentifier,
+    TextEdit,
+    Range,
+    Position,
+    SignatureHelp,
+    SignatureInformation,
+    ParameterInformation
+};
+use function LanguageServer\pathToUri;
+
+class SignatureHelpTest extends TestCase
+{
+    /**
+     * @var Server\TextDocument
+     */
+    private $textDocument;
+
+    /**
+     * @var PhpDocumentLoader
+     */
+    private $loader;
+
+    public function setUp()
+    {
+        $client = new LanguageClient(new MockProtocolStream, new MockProtocolStream);
+        $projectIndex = new ProjectIndex(new Index, new DependenciesIndex);
+        $definitionResolver = new DefinitionResolver($projectIndex);
+        $contentRetriever = new FileSystemContentRetriever;
+        $this->loader = new PhpDocumentLoader($contentRetriever, $projectIndex, $definitionResolver);
+        $this->textDocument = new Server\TextDocument($this->loader, $definitionResolver, $client, $projectIndex);
+    }
+
+    /**
+     * @dataProvider signatureHelpProvider
+     */
+    public function testSignatureHelp(Position $position, SignatureHelp $expectedSignature)
+    {
+        $callsUri = pathToUri(__DIR__ . '/../../../fixtures/signature_help/calls.php');
+        $this->loader->open($callsUri, file_get_contents($callsUri));
+        $signatureHelp = $this->textDocument->signatureHelp(
+            new TextDocumentIdentifier($callsUri),
+            $position
+        )->wait();
+        $this->assertEquals($expectedSignature, $signatureHelp);
+    }
+
+    public function signatureHelpProvider(): array
+    {
+        return [
+            'member call' => [
+                new Position(48, 9),
+                $this->createSignatureHelp([
+                    'label' => '(\\Foo\\SomethingElse $a, int|null $b = null)',
+                    'documentation' => 'Function doc',
+                    'parameters' => [
+                        [
+                            'label' => '\\Foo\\SomethingElse $a',
+                            'documentation' => 'A param with a different doc type',
+                        ],
+                        [
+                            'label' => 'int|null $b = null',
+                            'documentation' => 'Param with default value',
+                        ],
+                    ],
+                    'activeSignature' => 0,
+                    'activeParameter' => 0,
+                ]),
+            ],
+            'member call 2nd param active' => [
+                new Position(49, 11),
+                $this->createSignatureHelp([
+                    'label' => '(\\Foo\\SomethingElse $a, int|null $b = null)',
+                    'documentation' => 'Function doc',
+                    'parameters' => [
+                        [
+                            'label' => '\\Foo\\SomethingElse $a',
+                            'documentation' => 'A param with a different doc type',
+                        ],
+                        [
+                            'label' => 'int|null $b = null',
+                            'documentation' => 'Param with default value',
+                        ],
+                    ],
+                    'activeSignature' => 0,
+                    'activeParameter' => 1,
+                ]),
+            ],
+            'method with no params' => [
+                new Position(50, 9),
+                $this->createSignatureHelp([
+                    'label' => '()',
+                    'documentation' => 'Method with no params',
+                    'parameters' => [],
+                    'activeSignature' => 0,
+                    'activeParameter' => 0,
+                ]),
+            ],
+            'constructor' => [
+                new Position(47, 14),
+                $this->createSignatureHelp([
+                    'label' => '(string $first, int $second, \Foo\Test $third)',
+                    'documentation' => 'Constructor comment goes here',
+                    'parameters' => [
+                        [
+                            'label' => 'string $first',
+                            'documentation' => 'First param',
+
+                        ],
+                        [
+                            'label' => 'int $second',
+                            'documentation' => 'Second param',
+                        ],
+                        [
+                            'label' => '\Foo\Test $third',
+                            'documentation' => 'Third param with a longer description',
+                        ],
+                    ],
+                    'activeSignature' => 0,
+                    'activeParameter' => 0,
+                ]),
+            ],
+            'global function' => [
+                new Position(52, 4),
+                $this->createSignatureHelp([
+                    'label' => '(int $i, bool $b = false)',
+                    'documentation' => null,
+                    'parameters' => [
+                        [
+                            'label' => 'int $i',
+                            'documentation' => 'Global function param one',
+                        ],
+                        [
+                            'label' => 'bool $b = false',
+                            'documentation' => 'Default false param',
+                        ],
+                    ],
+                    'activeSignature' => 0,
+                    'activeParameter' => 0,
+                ]),
+            ],
+            'static method' => [
+                new Position(54, 10),
+                $this->createSignatureHelp([
+                    'label' => '(mixed $a)',
+                    'documentation' => null,
+                    'parameters' => [
+                        [
+                            'label' => 'mixed $a',
+                            'documentation' => null,
+                        ],
+                    ],
+                    'activeSignature' => 0,
+                    'activeParameter' => 0,
+                ]),
+            ],
+        ];
+    }
+
+    private function createSignatureHelp(array $info): SignatureHelp
+    {
+        $params = [];
+        foreach ($info['parameters'] as $param) {
+            $paramInfo = new ParameterInformation();
+            $paramInfo->label = $param['label'];
+            $paramInfo->documentation = $param['documentation'];
+            $params[] = $paramInfo;
+        }
+        $signature = new SignatureInformation();
+        $signature->label = $info['label'];
+        $signature->documentation = $info['documentation'];
+        $signature->parameters = $params;
+        $help = new SignatureHelp();
+        $help->signatures = [$signature];
+        $help->activeSignature = $info['activeSignature'];
+        $help->activeParameter = $info['activeParameter'];
+        return $help;
+    }
+}