diff --git a/.changeset/chatty-singers-sin.md b/.changeset/chatty-singers-sin.md
new file mode 100644
index 0000000000..f69bc97454
--- /dev/null
+++ b/.changeset/chatty-singers-sin.md
@@ -0,0 +1,5 @@
+---
+'svelte': patch
+---
+
+fix: mark pseudo classes nested inside `:not` as used
diff --git a/packages/svelte/src/compiler/phases/2-analyze/css/css-analyze.js b/packages/svelte/src/compiler/phases/2-analyze/css/css-analyze.js
index 38551f328f..1dd2d9ae7c 100644
--- a/packages/svelte/src/compiler/phases/2-analyze/css/css-analyze.js
+++ b/packages/svelte/src/compiler/phases/2-analyze/css/css-analyze.js
@@ -150,8 +150,9 @@ const css_visitors = {
 			// So that nested selectors like `:root:not(.x)` are not marked as unused
 			for (const child of node.selectors) {
 				walk(/** @type {Css.Node} */ (child), null, {
-					ComplexSelector(node) {
+					ComplexSelector(node, context) {
 						node.metadata.used = true;
+						context.next();
 					}
 				});
 			}
diff --git a/packages/svelte/src/compiler/phases/2-analyze/css/css-prune.js b/packages/svelte/src/compiler/phases/2-analyze/css/css-prune.js
index bf0fd27566..bfb83d3e02 100644
--- a/packages/svelte/src/compiler/phases/2-analyze/css/css-prune.js
+++ b/packages/svelte/src/compiler/phases/2-analyze/css/css-prune.js
@@ -531,7 +531,12 @@ function relative_selector_might_apply_to_node(relative_selector, rule, element,
 				// with descendants, in which case we scope them all.
 				if (name === 'not' && selector.args) {
 					for (const complex_selector of selector.args.children) {
-						complex_selector.metadata.used = true;
+						walk(complex_selector, null, {
+							ComplexSelector(node, context) {
+								node.metadata.used = true;
+								context.next();
+							}
+						});
 						const relative = truncate(complex_selector);
 
 						if (complex_selector.children.length > 1) {
diff --git a/packages/svelte/tests/css/samples/not-selector/expected.css b/packages/svelte/tests/css/samples/not-selector/expected.css
index ea0b3aacac..1b0db0ff4b 100644
--- a/packages/svelte/tests/css/samples/not-selector/expected.css
+++ b/packages/svelte/tests/css/samples/not-selector/expected.css
@@ -29,3 +29,7 @@
 	span.svelte-xyz:not(:focus) {
 		color: green;
 	}
+
+	p.svelte-xyz:not(:has(span)) {
+		color: green;
+	}
diff --git a/packages/svelte/tests/css/samples/not-selector/input.svelte b/packages/svelte/tests/css/samples/not-selector/input.svelte
index 3a786530a2..da8f4579c2 100644
--- a/packages/svelte/tests/css/samples/not-selector/input.svelte
+++ b/packages/svelte/tests/css/samples/not-selector/input.svelte
@@ -36,4 +36,8 @@
 	span:not(:focus) {
 		color: green;
 	}
+
+	p:not(:has(span)) {
+		color: green;
+	}
 </style>
\ No newline at end of file