diff --git a/.changeset/mighty-banks-mate.md b/.changeset/mighty-banks-mate.md
new file mode 100644
index 00000000000..3d36984f5f0
--- /dev/null
+++ b/.changeset/mighty-banks-mate.md
@@ -0,0 +1,7 @@
+---
+'@tanstack/query-devtools': patch
+---
+
+`setupStyleSheet` now sets `window.__nonce__` when a `styleNonce` is provided.
+
+The devtools use [goober](https://goober.js.org/) for CSS-in-JS, which reads `window.__nonce__` every time it creates or accesses its style element. Without this, goober overwrote the nonce with `undefined`, causing CSP violations even when `styleNonce` was correctly passed to `<ReactQueryDevtools>`.
diff --git a/packages/query-devtools/src/__tests__/utils.test.ts b/packages/query-devtools/src/__tests__/utils.test.ts
index 07dff9ece4d..e71829a79ce 100644
--- a/packages/query-devtools/src/__tests__/utils.test.ts
+++ b/packages/query-devtools/src/__tests__/utils.test.ts
@@ -982,6 +982,7 @@ describe('Utils tests', () => {
   describe('setupStyleSheet', () => {
     afterEach(() => {
       document.head.querySelector('#_goober')?.remove()
+      delete (window as any).__nonce__
     })
 
     it('should not insert any style tag when "nonce" is missing', () => {
@@ -1042,6 +1043,18 @@ describe('Utils tests', () => {
       expect(styleTags).toHaveLength(1)
       expect(styleTags[0]?.getAttribute('nonce')).toBe('first-nonce')
     })
+
+    it('should set window.__nonce__ so goober preserves the nonce on its style element', () => {
+      setupStyleSheet('test-nonce')
+
+      expect((window as any).__nonce__).toBe('test-nonce')
+    })
+
+    it('should not set window.__nonce__ when nonce is missing', () => {
+      setupStyleSheet()
+
+      expect((window as any).__nonce__).toBeUndefined()
+    })
   })
 
   describe('sortFns', () => {
diff --git a/packages/query-devtools/src/utils.tsx b/packages/query-devtools/src/utils.tsx
index 9a826cd21e3..d87c368c95e 100644
--- a/packages/query-devtools/src/utils.tsx
+++ b/packages/query-devtools/src/utils.tsx
@@ -306,6 +306,12 @@ export const deleteNestedDataByPath = (
 // Adds a nonce to the style tag if needed
 export const setupStyleSheet = (nonce?: string, target?: ShadowRoot) => {
   if (!nonce) return
+
+  // Goober reads window.__nonce__ every time it creates or accesses its style
+  // element (e.nonce = window.__nonce__). Without this, goober overwrites the
+  // nonce we set on the pre-created element with undefined, clearing it.
+  ;(window as any).__nonce__ = nonce
+
   const styleExists =
     document.querySelector('#_goober') || target?.querySelector('#_goober')