diff --git a/packages/block-library/src/site-title/block.json b/packages/block-library/src/site-title/block.json
index 518b458184e94..95d8deb1e43b9 100644
--- a/packages/block-library/src/site-title/block.json
+++ b/packages/block-library/src/site-title/block.json
@@ -62,6 +62,12 @@
 		},
 		"interactivity": {
 			"clientNavigation": true
+		},
+		"__experimentalBorder": {
+			"radius": true,
+			"color": true,
+			"width": true,
+			"style": true
 		}
 	},
 	"editorStyle": "wp-block-site-title-editor",
diff --git a/packages/block-library/src/site-title/style.scss b/packages/block-library/src/site-title/style.scss
index 337c82f79ad35..f292326cc3259 100644
--- a/packages/block-library/src/site-title/style.scss
+++ b/packages/block-library/src/site-title/style.scss
@@ -1,3 +1,8 @@
-:root :where(.wp-block-site-title a) {
-	color: inherit;
+.wp-block-site-title {
+	// This block has customizable padding, border-box makes that more predictable.
+	box-sizing: border-box;
+
+	:where(a) {
+		color: inherit;
+	}
 }