diff --git a/src/wp-includes/l10n.php b/src/wp-includes/l10n.php
index ba856491af..0ad4e01ba7 100644
--- a/src/wp-includes/l10n.php
+++ b/src/wp-includes/l10n.php
@@ -88,7 +88,7 @@ function get_locale() {
  */
 function get_user_locale( $user_id = 0 ) {
 	$user = false;
-	if ( 0 === $user_id ) {
+	if ( 0 === $user_id && function_exists( 'wp_get_current_user' ) ) {
 		$user = wp_get_current_user();
 	} elseif ( $user_id instanceof WP_User ) {
 		$user = $user_id;
@@ -710,7 +710,7 @@ function load_plugin_textdomain( $domain, $deprecated = false, $plugin_rel_path
 	 * @param string $locale The plugin's current locale.
 	 * @param string $domain Text domain. Unique identifier for retrieving translated strings.
 	 */
-	$locale = apply_filters( 'plugin_locale', get_locale(), $domain );
+	$locale = apply_filters( 'plugin_locale', is_admin() ? get_user_locale() : get_locale(), $domain );
 
 	$mofile = $domain . '-' . $locale . '.mo';
 
@@ -744,7 +744,7 @@ function load_plugin_textdomain( $domain, $deprecated = false, $plugin_rel_path
  */
 function load_muplugin_textdomain( $domain, $mu_plugin_rel_path = '' ) {
 	/** This filter is documented in wp-includes/l10n.php */
-	$locale = apply_filters( 'plugin_locale', get_locale(), $domain );
+	$locale = apply_filters( 'plugin_locale', is_admin() ? get_user_locale() : get_locale(), $domain );
 
 	$mofile = $domain . '-' . $locale . '.mo';
 
@@ -783,7 +783,7 @@ function load_theme_textdomain( $domain, $path = false ) {
 	 * @param string $locale The theme's current locale.
 	 * @param string $domain Text domain. Unique identifier for retrieving translated strings.
 	 */
-	$locale = apply_filters( 'theme_locale', get_locale(), $domain );
+	$locale = apply_filters( 'theme_locale', is_admin() ? get_user_locale() : get_locale(), $domain );
 
 	$mofile = $domain . '-' . $locale . '.mo';
 
@@ -865,7 +865,7 @@ function _load_textdomain_just_in_time( $domain ) {
 		}
 	}
 
-	$locale = get_locale();
+	$locale = is_admin() ? get_user_locale() : get_locale();
 	$mofile = "{$domain}-{$locale}.mo";
 
 	if ( in_array( WP_LANG_DIR . '/plugins/' . $mofile, $cached_mofiles ) ) {
diff --git a/tests/phpunit/tests/l10n/loadTextdomain.php b/tests/phpunit/tests/l10n/loadTextdomain.php
index ec26281491..a44f09a7fd 100644
--- a/tests/phpunit/tests/l10n/loadTextdomain.php
+++ b/tests/phpunit/tests/l10n/loadTextdomain.php
@@ -6,6 +6,14 @@
  */
 class Tests_L10n_loadTextdomain extends WP_UnitTestCase {
 	protected $locale;
+	protected static $user_id;
+
+	public static function wpSetUpBeforeClass( $factory ) {
+		self::$user_id = $factory->user->create( array(
+			'role'   => 'administrator',
+			'locale' => 'de_DE',
+		) );
+	}
 
 	public function setUp() {
 		parent::setUp();
@@ -183,15 +191,57 @@ class Tests_L10n_loadTextdomain extends WP_UnitTestCase {
 		$this->assertSame( get_locale(), $this->locale );
 	}
 
+	/**
+	 * @ticket 38485
+	 */
+	public function test_load_muplugin_textdomain_user_locale() {
+		set_current_screen( 'dashboard' );
+		wp_set_current_user( self::$user_id );
+
+		load_muplugin_textdomain( 'wp-tests-domain' );
+
+		set_current_screen( 'front' );
+
+		$this->assertSame( get_user_locale(), $this->locale );
+	}
+
 	public function test_load_plugin_textdomain_site_locale() {
 		load_plugin_textdomain( 'wp-tests-domain' );
 
 		$this->assertSame( get_locale(), $this->locale );
 	}
 
+	/**
+	 * @ticket 38485
+	 */
+	public function test_load_plugin_textdomain_user_locale() {
+		set_current_screen( 'dashboard' );
+		wp_set_current_user( self::$user_id );
+
+		load_plugin_textdomain( 'wp-tests-domain' );
+
+		set_current_screen( 'front' );
+
+		$this->assertSame( get_user_locale(), $this->locale );
+	}
+
 	public function test_load_theme_textdomain_site_locale() {
 		load_theme_textdomain( 'wp-tests-domain' );
 
 		$this->assertSame( get_locale(), $this->locale );
 	}
+
+	/**
+	 * @ticket 38485
+	 */
+	public function test_load_theme_textdomain_user_locale() {
+		set_current_screen( 'dashboard' );
+		wp_set_current_user( self::$user_id );
+
+		load_theme_textdomain( 'wp-tests-domain' );
+
+		set_current_screen( 'front' );
+
+		$this->assertSame( get_user_locale(), $this->locale );
+	}
 }
diff --git a/tests/phpunit/tests/l10n/loadTextdomainJustInTime.php b/tests/phpunit/tests/l10n/loadTextdomainJustInTime.php
index 57aca144d3..f0d7b5528f 100644
--- a/tests/phpunit/tests/l10n/loadTextdomainJustInTime.php
+++ b/tests/phpunit/tests/l10n/loadTextdomainJustInTime.php
@@ -5,9 +5,16 @@
  * @group i18n
  */
 class Tests_L10n_loadTextdomainJustInTime extends WP_UnitTestCase {
+	protected $orig_theme_dir;
+	protected $theme_root;
+	protected static $user_id;
 
-	private $orig_theme_dir;
-	private $theme_root;
+	public static function wpSetUpBeforeClass( $factory ) {
+		self::$user_id = $factory->user->create( array(
+			'role'   => 'administrator',
+			'locale' => 'de_DE',
+		) );
+	}
 
 	public function setUp() {
 		parent::setUp();
@@ -171,4 +178,38 @@ class Tests_L10n_loadTextdomainJustInTime extends WP_UnitTestCase {
 
 		$this->assertSame( 'Das ist ein Dummy Theme', $expected );
 	}
+
+	/**
+	 * @ticket 38485
+	 */
+	public function test_plugin_translation_with_user_locale() {
+		require_once DIR_TESTDATA . '/plugins/internationalized-plugin.php';
+
+		set_current_screen( 'dashboard' );
+		wp_set_current_user( self::$user_id );
+
+		$expected = i18n_plugin_test();
+
+		set_current_screen( 'front' );
+
+		$this->assertSame( 'Das ist ein Dummy Plugin', $expected );
+	}
+
+	/**
+	 * @ticket 38485
+	 */
+	public function test_theme_translation_with_user_locale() {
+		switch_theme( 'internationalized-theme' );
+		set_current_screen( 'dashboard' );
+		wp_set_current_user( self::$user_id );
+
+		require_once get_stylesheet_directory() . '/functions.php';
+
+		$expected = i18n_theme_test();
+
+		set_current_screen( 'front' );
+		switch_theme( WP_DEFAULT_THEME );
+
+		$this->assertSame( 'Das ist ein Dummy Theme', $expected );
+	}
 }