diff --git a/src/Rector/Contrib/PHPUnit/SpecificMethodBoolNullRector.php b/src/Rector/Contrib/PHPUnit/SpecificMethodBoolNullRector.php
new file mode 100644
index 00000000000..63f7b9177e6
--- /dev/null
+++ b/src/Rector/Contrib/PHPUnit/SpecificMethodBoolNullRector.php
@@ -0,0 +1,78 @@
+<?php declare(strict_types=1);
+
+namespace Rector\Rector\Contrib\PHPUnit;
+
+use PhpParser\Node;
+use PhpParser\Node\Expr\ConstFetch;
+use PhpParser\Node\Expr\MethodCall;
+use PhpParser\Node\Identifier;
+use Rector\NodeAnalyzer\MethodCallAnalyzer;
+use Rector\Rector\AbstractRector;
+
+/**
+ * Before:
+ * - $this->assertSame(null, $anything);
+ *
+ * After:
+ * - $this->assertNull($anything);
+ */
+final class SpecificMethodBoolNullRector extends AbstractRector
+{
+    /**
+     * @var MethodCallAnalyzer
+     */
+    private $methodCallAnalyzer;
+
+    /**
+     * @var string|null
+     */
+    private $activeFuncCallName;
+
+    public function __construct(MethodCallAnalyzer $methodCallAnalyzer)
+    {
+        $this->methodCallAnalyzer = $methodCallAnalyzer;
+    }
+
+    public function isCandidate(Node $node): bool
+    {
+        $this->activeFuncCallName = null;
+
+        if (! $this->methodCallAnalyzer->isTypesAndMethods(
+            $node,
+            ['PHPUnit\Framework\TestCase', 'PHPUnit_Framework_TestCase'],
+            ['assertSame']
+        )) {
+            return false;
+        }
+
+        /** @var MethodCall $methodCallNode */
+        $methodCallNode = $node;
+
+        $firstArgumentValue = $methodCallNode->args[0]->value;
+        if (! $firstArgumentValue instanceof ConstFetch) {
+            return false;
+        }
+
+        $costName = $firstArgumentValue->name->toString();
+        if ($costName === 'null') {
+            return true;
+        }
+
+        return false;
+    }
+
+    /**
+     * @param MethodCall $methodCallNode
+     */
+    public function refactor(Node $methodCallNode): ?Node
+    {
+        $methodCallNode->name = new Identifier('assertNull');
+
+        $methodArguments = $methodCallNode->args;
+        array_shift($methodArguments);
+
+        $methodCallNode->args = $methodCallNode;
+
+        return $methodCallNode;
+    }
+}
diff --git a/src/config/level/phpunit/phpunit60.yml b/src/config/level/phpunit/phpunit60.yml
index f3ffc3b3518..76b71d5f945 100644
--- a/src/config/level/phpunit/phpunit60.yml
+++ b/src/config/level/phpunit/phpunit60.yml
@@ -2,6 +2,7 @@ rectors:
     Rector\Rector\Contrib\PHPUnit\ExceptionAnnotationRector: ~
     Rector\Rector\Contrib\PHPUnit\GetMockRector: ~
     Rector\Rector\Contrib\PHPUnit\SpecificMethodRector: ~
+    Rector\Rector\Contrib\PHPUnit\SpecificMethodBoolNullRector: ~
 
     # ref. https://github.com/sebastianbergmann/phpunit/compare/5.7.9...6.0.0
     Rector\Rector\Dynamic\PseudoNamespaceToNamespaceRector:
diff --git a/tests/Rector/Contrib/PHPUnit/SpecificMethodBoolNullRector/Correct/correct.php.inc b/tests/Rector/Contrib/PHPUnit/SpecificMethodBoolNullRector/Correct/correct.php.inc
new file mode 100644
index 00000000000..ce1c81161ef
--- /dev/null
+++ b/tests/Rector/Contrib/PHPUnit/SpecificMethodBoolNullRector/Correct/correct.php.inc
@@ -0,0 +1,9 @@
+<?php declare(strict_types=1);
+
+final class MyTest extends \PHPUnit\Framework\TestCase
+{
+    public function test()
+    {
+        $this->assertNull('second argument');
+    }
+}
diff --git a/tests/Rector/Contrib/PHPUnit/SpecificMethodBoolNullRector/Test.php b/tests/Rector/Contrib/PHPUnit/SpecificMethodBoolNullRector/Test.php
new file mode 100644
index 00000000000..b4651a63b46
--- /dev/null
+++ b/tests/Rector/Contrib/PHPUnit/SpecificMethodBoolNullRector/Test.php
@@ -0,0 +1,25 @@
+<?php declare(strict_types=1);
+
+namespace Rector\Tests\Rector\Contrib\PHPUnit\SpecificMethodBoolNullRector;
+
+use Rector\Rector\Contrib\PHPUnit\SpecificMethodBoolNullRector;
+use Rector\Testing\PHPUnit\AbstractRectorTestCase;
+
+final class Test extends AbstractRectorTestCase
+{
+    public function test(): void
+    {
+        $this->doTestFileMatchesExpectedContent(
+            __DIR__ . '/Wrong/wrong.php.inc',
+            __DIR__ . '/Correct/correct.php.inc'
+        );
+    }
+
+    /**
+     * @return string[]
+     */
+    protected function getRectorClasses(): array
+    {
+        return [SpecificMethodBoolNullRector::class];
+    }
+}
diff --git a/tests/Rector/Contrib/PHPUnit/SpecificMethodBoolNullRector/Wrong/wrong.php.inc b/tests/Rector/Contrib/PHPUnit/SpecificMethodBoolNullRector/Wrong/wrong.php.inc
new file mode 100644
index 00000000000..8da58ea171c
--- /dev/null
+++ b/tests/Rector/Contrib/PHPUnit/SpecificMethodBoolNullRector/Wrong/wrong.php.inc
@@ -0,0 +1,9 @@
+<?php declare(strict_types=1);
+
+final class MyTest extends \PHPUnit\Framework\TestCase
+{
+    public function test()
+    {
+        $this->assertSame(null, 'second argument');
+    }
+}