diff --git a/app/code/Magento/Captcha/Test/Unit/Observer/CheckUserLoginBackendObserverTest.php b/app/code/Magento/Captcha/Test/Unit/Observer/CheckUserLoginBackendObserverTest.php
new file mode 100644
index 0000000000000..6966bd4cce7f9
--- /dev/null
+++ b/app/code/Magento/Captcha/Test/Unit/Observer/CheckUserLoginBackendObserverTest.php
@@ -0,0 +1,137 @@
+<?php
+/**
+ * Copyright © Magento, Inc. All rights reserved.
+ * See COPYING.txt for license details.
+ */
+declare(strict_types=1);
+
+namespace Magento\Captcha\Test\Unit\Observer;
+
+use Magento\Captcha\Helper\Data;
+use Magento\Captcha\Model\DefaultModel;
+use Magento\Captcha\Observer\CaptchaStringResolver;
+use Magento\Captcha\Observer\CheckUserLoginBackendObserver;
+use Magento\Framework\App\RequestInterface;
+use Magento\Framework\Event;
+use Magento\Framework\Event\Observer;
+use Magento\Framework\Message\ManagerInterface;
+use PHPUnit\Framework\TestCase;
+use PHPUnit_Framework_MockObject_MockObject as MockObject;
+
+/**
+ * Class CheckUserLoginBackendObserverTest
+ */
+class CheckUserLoginBackendObserverTest extends TestCase
+{
+    /**
+     * @var CheckUserLoginBackendObserver
+     */
+    private $observer;
+
+    /**
+     * @var ManagerInterface|MockObject
+     */
+    private $messageManagerMock;
+
+    /**
+     * @var CaptchaStringResolver|MockObject
+     */
+    private $captchaStringResolverMock;
+
+    /**
+     * @var RequestInterface|MockObject
+     */
+    private $requestMock;
+
+    /**
+     * @var Data|MockObject
+     */
+    private $helperMock;
+
+    /**
+     * Set Up
+     *
+     * @return void
+     */
+    protected function setUp()
+    {
+        $this->helperMock = $this->createMock(Data::class);
+        $this->messageManagerMock = $this->createMock(ManagerInterface::class);
+        $this->captchaStringResolverMock = $this->createMock(CaptchaStringResolver::class);
+        $this->requestMock = $this->createMock(RequestInterface::class);
+
+        $this->observer = new CheckUserLoginBackendObserver(
+            $this->helperMock,
+            $this->captchaStringResolverMock,
+            $this->requestMock
+        );
+    }
+
+    /**
+     * Test check user login in backend with correct captcha
+     *
+     * @dataProvider requiredCaptchaDataProvider
+     * @param bool $isRequired
+     * @return void
+     */
+    public function testCheckOnBackendLoginWithCorrectCaptcha(bool $isRequired)
+    {
+        $formId = 'backend_login';
+        $login = 'admin';
+        $captchaValue = 'captcha-value';
+
+        /** @var Observer|MockObject $observerMock */
+        $observerMock = $this->createPartialMock(Observer::class, ['getEvent']);
+        $eventMock = $this->createPartialMock(Event::class, ['getUsername']);
+        $captcha = $this->createMock(DefaultModel::class);
+
+        $eventMock->method('getUsername')->willReturn('admin');
+        $observerMock->method('getEvent')->willReturn($eventMock);
+        $captcha->method('isRequired')->with($login)->willReturn($isRequired);
+        $captcha->method('isCorrect')->with($captchaValue)->willReturn(true);
+        $this->helperMock->method('getCaptcha')->with($formId)->willReturn($captcha);
+        $this->captchaStringResolverMock->method('resolve')->with($this->requestMock, $formId)
+            ->willReturn($captchaValue);
+
+        $this->observer->execute($observerMock);
+    }
+
+    /**
+     * @return array
+     */
+    public function requiredCaptchaDataProvider(): array
+    {
+        return [
+            [true],
+            [false]
+        ];
+    }
+
+    /**
+     * Test check user login in backend with wrong captcha
+     *
+     * @return void
+     * @expectedException \Magento\Framework\Exception\Plugin\AuthenticationException
+     */
+    public function testCheckOnBackendLoginWithWrongCaptcha()
+    {
+        $formId = 'backend_login';
+        $login = 'admin';
+        $captchaValue = 'captcha-value';
+
+        /** @var Observer|MockObject $observerMock */
+        $observerMock = $this->createPartialMock(Observer::class, ['getEvent']);
+        $eventMock = $this->createPartialMock(Event::class, ['getUsername']);
+        $captcha = $this->createMock(DefaultModel::class);
+
+        $eventMock->method('getUsername')->willReturn($login);
+        $observerMock->method('getEvent')->willReturn($eventMock);
+        $captcha->method('isRequired')->with($login)->willReturn(true);
+        $captcha->method('isCorrect')->with($captchaValue)->willReturn(false);
+        $this->helperMock->method('getCaptcha')->with($formId)->willReturn($captcha);
+        $this->captchaStringResolverMock->method('resolve')->with($this->requestMock, $formId)
+            ->willReturn($captchaValue);
+
+        $this->observer->execute($observerMock);
+    }
+}