diff --git a/.changeset/heavy-coins-tickle.md b/.changeset/heavy-coins-tickle.md
new file mode 100644
index 0000000000..03b8eb3c96
--- /dev/null
+++ b/.changeset/heavy-coins-tickle.md
@@ -0,0 +1,5 @@
+---
+'@shopify/hydrogen': minor
+---
+
+💥 Change the behaviour of `createContentSecurityPolicy` where the custom rules passed in will extends the default Shopify and development domains instead of overriding them.
diff --git a/packages/hydrogen/src/csp/csp.test.ts b/packages/hydrogen/src/csp/csp.test.ts
index d36e1e75ba..9f2783e90c 100644
--- a/packages/hydrogen/src/csp/csp.test.ts
+++ b/packages/hydrogen/src/csp/csp.test.ts
@@ -25,28 +25,20 @@ describe('createContentSecurityPolicy', () => {
   it('adds custom directives', () => {
     expect(
       createContentSecurityPolicy({
-        styleSrc: [
-          "'self'",
-          'https://cdn.shopify.com',
-          'https://some-custom-css.cdn',
-        ],
+        styleSrc: ['https://some-custom-css.cdn'],
       }).header,
     ).toBe(
-      `base-uri 'self'; default-src 'self' 'nonce-somenonce' https://cdn.shopify.com https://shopify.com; frame-ancestors none; style-src 'self' https://cdn.shopify.com https://some-custom-css.cdn; connect-src 'self' https://monorail-edge.shopifysvc.com`,
+      `base-uri 'self'; default-src 'self' 'nonce-somenonce' https://cdn.shopify.com https://shopify.com; frame-ancestors none; style-src https://some-custom-css.cdn 'self' 'unsafe-inline' https://cdn.shopify.com; connect-src 'self' https://monorail-edge.shopifysvc.com`,
     );
   });
 
   it('adds nonce to custom directives', () => {
     expect(
       createContentSecurityPolicy({
-        scriptSrc: [
-          "'self'",
-          'https://cdn.shopify.com',
-          'https://some-custom-css.cdn',
-        ],
+        scriptSrc: ['https://some-custom-css.cdn'],
       }).header,
     ).toBe(
-      `base-uri 'self'; default-src 'self' 'nonce-somenonce' https://cdn.shopify.com https://shopify.com; frame-ancestors none; style-src 'self' 'unsafe-inline' https://cdn.shopify.com; connect-src 'self' https://monorail-edge.shopifysvc.com; script-src 'self' https://cdn.shopify.com https://some-custom-css.cdn 'nonce-somenonce'`,
+      `base-uri 'self'; default-src 'self' 'nonce-somenonce' https://cdn.shopify.com https://shopify.com; frame-ancestors none; style-src 'self' 'unsafe-inline' https://cdn.shopify.com; connect-src 'self' https://monorail-edge.shopifysvc.com; script-src https://some-custom-css.cdn 'nonce-somenonce'`,
     );
   });
 });
diff --git a/packages/hydrogen/src/csp/csp.ts b/packages/hydrogen/src/csp/csp.ts
index 61836fa449..38a0cc6d8e 100644
--- a/packages/hydrogen/src/csp/csp.ts
+++ b/packages/hydrogen/src/csp/csp.ts
@@ -79,6 +79,16 @@ function createCSPHeader(
 
   const combinedDirectives = Object.assign({}, defaultDirectives, directives);
 
+  //add defaults if it was override
+  for (const key in defaultDirectives) {
+    if (directives[key]) {
+      combinedDirectives[key] = addCspDirective(
+        directives[key],
+        defaultDirectives[key],
+      );
+    }
+  }
+
   // Make sure that at least script-src includes a nonce directive.
   // If someone doesn't want a nonce in their CSP, they probably
   // shouldn't use our utilities and just manually create their CSP.
@@ -98,3 +108,19 @@ function createCSPHeader(
     directives: combinedDirectives,
   });
 }
+
+function addCspDirective(
+  currentValue: string[] | string | boolean,
+  value: string[] | string | boolean,
+): boolean | string[] {
+  const normalizedValue = typeof value === 'string' ? [value] : value;
+  const normalizedCurrentValue = Array.isArray(currentValue)
+    ? currentValue
+    : [String(currentValue)];
+
+  const newValue = Array.isArray(normalizedValue)
+    ? [...normalizedCurrentValue, ...normalizedValue]
+    : normalizedValue;
+
+  return newValue;
+}