diff --git a/packages/block-library/src/site-tagline/block.json b/packages/block-library/src/site-tagline/block.json
index c2061726d62a9..25b3840cd663a 100644
--- a/packages/block-library/src/site-tagline/block.json
+++ b/packages/block-library/src/site-tagline/block.json
@@ -56,7 +56,14 @@
 		},
 		"interactivity": {
 			"clientNavigation": true
+		},
+		"__experimentalBorder": {
+			"radius": true,
+			"color": true,
+			"width": true,
+			"style": true
 		}
 	},
-	"editorStyle": "wp-block-site-tagline-editor"
+	"editorStyle": "wp-block-site-tagline-editor",
+	"style": "wp-block-site-tagline"
 }
diff --git a/packages/block-library/src/site-tagline/style.scss b/packages/block-library/src/site-tagline/style.scss
new file mode 100644
index 0000000000000..a22eeebb6e277
--- /dev/null
+++ b/packages/block-library/src/site-tagline/style.scss
@@ -0,0 +1,4 @@
+.wp-block-site-tagline {
+	// This block has customizable padding, border-box makes that more predictable.
+	box-sizing: border-box;
+}
diff --git a/packages/block-library/src/style.scss b/packages/block-library/src/style.scss
index 790e09535f4b6..112c0f4724f1b 100644
--- a/packages/block-library/src/style.scss
+++ b/packages/block-library/src/style.scss
@@ -47,6 +47,7 @@
 @import "./search/style.scss";
 @import "./separator/style.scss";
 @import "./site-logo/style.scss";
+@import "./site-tagline/style.scss";
 @import "./site-title/style.scss";
 @import "./social-links/style.scss";
 @import "./spacer/style.scss";