diff --git a/plugins/view-transitions/includes/admin.php b/plugins/view-transitions/includes/admin.php
index 83e81e45e3..c5132b7ab2 100644
--- a/plugins/view-transitions/includes/admin.php
+++ b/plugins/view-transitions/includes/admin.php
@@ -27,9 +27,12 @@ function plvt_print_view_transitions_admin_style(): void {
 	if ( ! isset( $options['enable_admin_transitions'] ) || true !== $options['enable_admin_transitions'] ) {
 		return;
 	}
+
+	$duration_seconds = absint( $options['default_transition_animation_duration'] ) / 1000;
 	?>
 <style>
 	@view-transition { navigation: auto; }
+	::view-transition-group(*) { animation-duration: <?php echo (int) $duration_seconds ; ?>s; }
 	#adminmenu > .menu-top { view-transition-name: attr(id type(<custom-ident>), none); }
 </style>
 	<?php
diff --git a/plugins/view-transitions/includes/settings.php b/plugins/view-transitions/includes/settings.php
index 4242dfc6de..ae4fe52f73 100644
--- a/plugins/view-transitions/includes/settings.php
+++ b/plugins/view-transitions/includes/settings.php
@@ -10,6 +10,23 @@
 if ( ! defined( 'ABSPATH' ) ) {
 	exit; // Exit if accessed directly.
 }
+
+
+/**
+ * Minimum allowed transition animation duration in milliseconds.
+ *
+ * @since n.e.x.t
+ * @var int
+ */
+const PLVT_MIN_ANIMATION_DURATION = 100;
+
+/**
+ * Maximum allowed transition animation duration in milliseconds.
+ *
+ * @since n.e.x.t
+ * @var int
+ */
+const PLVT_MAX_ANIMATION_DURATION = 5000;
 // @codeCoverageIgnoreEnd
 
 /**
@@ -135,9 +152,11 @@ function plvt_sanitize_setting( $input ): array {
 		$value['default_transition_animation'] = $input['default_transition_animation'];
 	}
 
-	// Handle default_transition_animation_duration separately.
+	// Handle default_transition_animation_duration with min/max bounds.
 	if ( isset( $input['default_transition_animation_duration'] ) ) {
-		$value['default_transition_animation_duration'] = absint( $input['default_transition_animation_duration'] );
+		$duration = absint( $input['default_transition_animation_duration'] );
+		// Clamp between min and max for sensible values.
+		$value['default_transition_animation_duration'] = max( PLVT_MIN_ANIMATION_DURATION, min( PLVT_MAX_ANIMATION_DURATION, $duration ) );
 	}
 
 	$selector_options = array(
@@ -193,6 +212,12 @@ function plvt_register_setting(): void {
 							'type'        => 'string',
 							'enum'        => array_keys( plvt_get_view_transition_animation_labels() ),
 						),
+						'default_transition_animation_duration' => array(
+							'description' => __( 'Duration of the view transition animation in milliseconds.', 'view-transitions' ),
+							'type'        => 'integer',
+							'minimum'     => PLVT_MIN_ANIMATION_DURATION,
+							'maximum'     => PLVT_MAX_ANIMATION_DURATION,
+						),
 					),
 					'additionalProperties' => false,
 				),
@@ -325,9 +350,14 @@ static function (): void {
 			'description' => __( 'Choose the animation that is used for the default view transition type.', 'view-transitions' ),
 		),
 		'default_transition_animation_duration' => array(
-			'section'     => 'plvt_view_transitions',
-			'title'       => __( 'Transition Animation Duration', 'view-transitions' ),
-			'description' => __( 'Control the duration of the view transition. Enter the value in milliseconds (e.g., 500, 1000, 2000).', 'view-transitions' ),
+			'section'      => 'plvt_view_transitions',
+			'title'        => __( 'Transition Animation Duration', 'view-transitions' ),
+			'description'  => __( 'Control the duration of the view transition. Enter the value in milliseconds (e.g., 500, 1000, 2000).', 'view-transitions' ),
+			'min'          => PLVT_MIN_ANIMATION_DURATION,
+			'max'          => PLVT_MAX_ANIMATION_DURATION,
+			'step'         => 50,
+			'unit'         => 'ms',
+			'show_seconds' => true,
 		),
 		'header_selector'                       => array(
 			'section'     => 'plvt_view_transitions',
@@ -473,10 +503,68 @@ function plvt_render_settings_field( array $args ): void {
 			<?php echo esc_html( $args['description'] ); ?>
 		</label>
 		<?php
+	} elseif ( 'number' === $type ) {
+		?>
+		<input
+			type="number"
+			id="<?php echo esc_attr( $args['label_for'] ); ?>"
+			name="<?php echo esc_attr( "plvt_view_transitions[{$args['field']}]" ); ?>"
+			value="<?php echo esc_attr( (string) $value ); ?>"
+			class="small-text"
+			<?php
+			if ( isset( $args['min'] ) ) {
+				?>
+				min="<?php echo esc_attr( (string) $args['min'] ); ?>"
+				<?php
+			}
+			if ( isset( $args['max'] ) ) {
+				?>
+				max="<?php echo esc_attr( (string) $args['max'] ); ?>"
+				<?php
+			}
+			if ( isset( $args['step'] ) ) {
+				?>
+				step="<?php echo esc_attr( (string) $args['step'] ); ?>"
+				<?php
+			}
+			if ( '' !== $args['description'] ) {
+				?>
+				aria-describedby="<?php echo esc_attr( $args['label_for'] . '-description' ); ?>"
+				<?php
+			}
+			?>
+		>
+		<?php
+		if ( isset( $args['unit'] ) && '' !== $args['unit'] ) {
+			?>
+			<span class="description">
+				<?php
+				if ( isset( $args['show_seconds'] ) && true === $args['show_seconds'] ) {
+					$seconds  = (int) $value / 1000;
+					$field_id = esc_attr( $args['label_for'] );
+					printf(
+						/* translators: 1: unit, 2: duration in seconds wrapped in a span for dynamic update */
+						esc_html__( '%1$s (%2$s)', 'view-transitions' ),
+						esc_html( $args['unit'] ),
+						'<span id="' . esc_attr( $args['label_for'] ) . '-seconds">' . esc_html( (string) $seconds ) . 's</span>'
+					);
+					wp_print_inline_script_tag(
+						sprintf(
+							'document.getElementById( %s ).addEventListener( "input", function( e ) { document.getElementById( %s ).textContent = ( parseInt( e.target.value, 10 ) / 1000 ) + "s"; } );',
+							wp_json_encode( $field_id ),
+							wp_json_encode( $field_id . '-seconds' )
+						)
+					);
+				} else {
+					echo esc_html( $args['unit'] );
+				}
+				?>
+			</span>
+			<?php
+		}
 	} else {
 		?>
 		<input
-			<?php echo ( 'number' === $type ) ? 'type="number"' : ''; ?>
 			id="<?php echo esc_attr( $args['label_for'] ); ?>"
 			name="<?php echo esc_attr( "plvt_view_transitions[{$args['field']}]" ); ?>"
 			value="<?php echo esc_attr( (string) $value ); ?>"
diff --git a/plugins/view-transitions/tests/test-admin.php b/plugins/view-transitions/tests/test-admin.php
new file mode 100644
index 0000000000..3edc8beca7
--- /dev/null
+++ b/plugins/view-transitions/tests/test-admin.php
@@ -0,0 +1,60 @@
+<?php
+/**
+ * Tests for the View Transitions plugin includes/admin.php file.
+ *
+ * @package view-transitions
+ * @group   view-transitions
+ */
+
+class Test_ViewTransitions_Admin extends WP_UnitTestCase {
+
+	/**
+	 * @covers ::plvt_print_view_transitions_admin_style
+	 */
+	public function test_plvt_print_view_transitions_admin_style_disabled(): void {
+		update_option( 'plvt_view_transitions', array( 'enable_admin_transitions' => false ) );
+
+		ob_start();
+		plvt_print_view_transitions_admin_style();
+		$output = ob_get_clean();
+
+		$this->assertEmpty( $output );
+	}
+
+	/**
+	 * @covers ::plvt_print_view_transitions_admin_style
+	 */
+	public function test_plvt_print_view_transitions_admin_style_enabled(): void {
+		update_option(
+			'plvt_view_transitions',
+			array(
+				'enable_admin_transitions'              => true,
+				'default_transition_animation_duration' => 500,
+			)
+		);
+
+		ob_start();
+		plvt_print_view_transitions_admin_style();
+		$output = ob_get_clean();
+
+		$this->assertStringContainsString( '@view-transition { navigation: auto; }', $output );
+		$this->assertStringContainsString( 'animation-duration: 0.5s', $output );
+	}
+
+	/**
+	 * @covers ::plvt_print_view_transitions_admin_style
+	 */
+	public function test_plvt_print_view_transitions_admin_style_uses_default_duration(): void {
+		update_option(
+			'plvt_view_transitions',
+			array( 'enable_admin_transitions' => true )
+		);
+
+		ob_start();
+		plvt_print_view_transitions_admin_style();
+		$output = ob_get_clean();
+
+		// Default duration is 400ms = 0.4s.
+		$this->assertStringContainsString( 'animation-duration: 0.4s', $output );
+	}
+}
diff --git a/plugins/view-transitions/tests/test-settings.php b/plugins/view-transitions/tests/test-settings.php
new file mode 100644
index 0000000000..93954fce1c
--- /dev/null
+++ b/plugins/view-transitions/tests/test-settings.php
@@ -0,0 +1,89 @@
+<?php
+/**
+ * Tests for the View Transitions plugin includes/settings.php file.
+ *
+ * @package view-transitions
+ * @group   view-transitions
+ */
+
+class Test_ViewTransitions_Settings extends WP_UnitTestCase {
+
+	/**
+	 * @covers ::plvt_sanitize_setting
+	 */
+	public function test_plvt_sanitize_setting_returns_defaults_for_invalid_input(): void {
+		$this->assertSame( plvt_get_setting_default(), plvt_sanitize_setting( null ) );
+		$this->assertSame( plvt_get_setting_default(), plvt_sanitize_setting( 'string' ) );
+		$this->assertSame( plvt_get_setting_default(), plvt_sanitize_setting( 123 ) );
+	}
+
+	/**
+	 * @covers ::plvt_sanitize_setting
+	 */
+	public function test_plvt_sanitize_setting_clamps_duration_minimum(): void {
+		$input  = array( 'default_transition_animation_duration' => 50 );
+		$result = plvt_sanitize_setting( $input );
+		$this->assertSame( PLVT_MIN_ANIMATION_DURATION, $result['default_transition_animation_duration'] );
+	}
+
+	/**
+	 * @covers ::plvt_sanitize_setting
+	 */
+	public function test_plvt_sanitize_setting_clamps_duration_maximum(): void {
+		$input  = array( 'default_transition_animation_duration' => 10000 );
+		$result = plvt_sanitize_setting( $input );
+		$this->assertSame( PLVT_MAX_ANIMATION_DURATION, $result['default_transition_animation_duration'] );
+	}
+
+	/**
+	 * @covers ::plvt_sanitize_setting
+	 */
+	public function test_plvt_sanitize_setting_accepts_valid_duration(): void {
+		$input  = array( 'default_transition_animation_duration' => 500 );
+		$result = plvt_sanitize_setting( $input );
+		$this->assertSame( 500, $result['default_transition_animation_duration'] );
+	}
+
+	/**
+	 * @covers ::plvt_sanitize_setting
+	 */
+	public function test_plvt_sanitize_setting_handles_negative_duration(): void {
+		$input  = array( 'default_transition_animation_duration' => -500 );
+		$result = plvt_sanitize_setting( $input );
+		// absint converts negative to positive, then clamps.
+		$this->assertSame( 500, $result['default_transition_animation_duration'] );
+	}
+
+	/**
+	 * @covers ::plvt_sanitize_setting
+	 */
+	public function test_plvt_sanitize_setting_handles_string_duration(): void {
+		$input  = array( 'default_transition_animation_duration' => '750' );
+		$result = plvt_sanitize_setting( $input );
+		$this->assertSame( 750, $result['default_transition_animation_duration'] );
+	}
+
+	/**
+	 * @covers ::plvt_get_setting_default
+	 */
+	public function test_plvt_get_setting_default_has_valid_duration(): void {
+		$defaults = plvt_get_setting_default();
+		$this->assertArrayHasKey( 'default_transition_animation_duration', $defaults );
+		$this->assertIsInt( $defaults['default_transition_animation_duration'] );
+		$this->assertGreaterThanOrEqual( PLVT_MIN_ANIMATION_DURATION, $defaults['default_transition_animation_duration'] );
+		$this->assertLessThanOrEqual( PLVT_MAX_ANIMATION_DURATION, $defaults['default_transition_animation_duration'] );
+	}
+
+	/**
+	 * @covers ::plvt_sanitize_setting
+	 */
+	public function test_plvt_sanitize_setting_validates_animation_type(): void {
+		$input  = array( 'default_transition_animation' => 'invalid-animation' );
+		$result = plvt_sanitize_setting( $input );
+		$this->assertSame( 'fade', $result['default_transition_animation'] );
+
+		$input  = array( 'default_transition_animation' => 'slide-from-right' );
+		$result = plvt_sanitize_setting( $input );
+		$this->assertSame( 'slide-from-right', $result['default_transition_animation'] );
+	}
+}
diff --git a/plugins/view-transitions/tests/test-theme.php b/plugins/view-transitions/tests/test-theme.php
index 7879c72f73..c675ccd903 100644
--- a/plugins/view-transitions/tests/test-theme.php
+++ b/plugins/view-transitions/tests/test-theme.php
@@ -48,4 +48,36 @@ public function test_plvt_load_view_transitions(): void {
 		$this->assertTrue( wp_style_is( 'plvt-view-transitions', 'registered' ) );
 		$this->assertTrue( wp_style_is( 'plvt-view-transitions', 'enqueued' ) );
 	}
+
+	/**
+	 * @covers ::plvt_inject_animation_duration
+	 */
+	public function test_plvt_inject_animation_duration_with_existing_css(): void {
+		$css    = '::view-transition-old(*) { animation-name: test; }';
+		$result = plvt_inject_animation_duration( $css, 500 );
+
+		$this->assertStringContainsString( '--plvt-view-transition-animation-duration: 0.5s', $result );
+		$this->assertStringContainsString( $css, $result );
+	}
+
+	/**
+	 * @covers ::plvt_inject_animation_duration
+	 */
+	public function test_plvt_inject_animation_duration_with_empty_css(): void {
+		$result = plvt_inject_animation_duration( '', 400 );
+
+		$this->assertStringContainsString( 'animation-duration: 0.4s', $result );
+		$this->assertStringNotContainsString( '--plvt-view-transition-animation-duration', $result );
+	}
+
+	/**
+	 * @covers ::plvt_inject_animation_duration
+	 */
+	public function test_plvt_inject_animation_duration_converts_milliseconds_to_seconds(): void {
+		$result = plvt_inject_animation_duration( '', 1000 );
+		$this->assertStringContainsString( '1s', $result );
+
+		$result = plvt_inject_animation_duration( '', 250 );
+		$this->assertStringContainsString( '0.25s', $result );
+	}
 }