diff --git a/.changeset/solid-eagles-mate.md b/.changeset/solid-eagles-mate.md
new file mode 100644
index 0000000000..a5ac5e6b46
--- /dev/null
+++ b/.changeset/solid-eagles-mate.md
@@ -0,0 +1,8 @@
+---
+"@pnpm/workspace.manifest-writer": patch
+"pnpm": patch
+---
+
+Fix YAML formatting preservation in `pnpm-workspace.yaml` when running commands like `pnpm update`. Previously, quotes and other formatting were lost even when catalog values didn't change.
+
+Closes #10425
diff --git a/workspace/manifest-writer/src/index.ts b/workspace/manifest-writer/src/index.ts
index e5e376fbe0..e523efe3b8 100644
--- a/workspace/manifest-writer/src/index.ts
+++ b/workspace/manifest-writer/src/index.ts
@@ -115,13 +115,14 @@ function addCatalogs (manifest: Partial<WorkspaceManifest>, newCatalogs: Catalog
       }
 
       targetCatalog ??= {}
-      targetCatalog[dependencyName] = specifier
+      if (targetCatalog[dependencyName] !== specifier) {
+        targetCatalog[dependencyName] = specifier
+        shouldBeUpdated = true
+      }
     }
 
     if (targetCatalog == null) continue
 
-    shouldBeUpdated = true
-
     if (targetCatalogWasNil) {
       if (catalogName === 'default') {
         manifest.catalog = targetCatalog
diff --git a/workspace/manifest-writer/test/updateWorkspaceManifest.test.ts b/workspace/manifest-writer/test/updateWorkspaceManifest.test.ts
index 6270509cfe..c1d94ba600 100644
--- a/workspace/manifest-writer/test/updateWorkspaceManifest.test.ts
+++ b/workspace/manifest-writer/test/updateWorkspaceManifest.test.ts
@@ -98,3 +98,58 @@ test('updateWorkspaceManifest updates allowBuilds', async () => {
     },
   })
 })
+
+test('updateWorkspaceManifest adds a new catalog', async () => {
+  const dir = tempDir(false)
+  const filePath = path.join(dir, WORKSPACE_MANIFEST_FILENAME)
+
+  fs.writeFileSync(filePath, 'packages:\n  - \'*\'\n')
+
+  await updateWorkspaceManifest(dir, {
+    updatedCatalogs: {
+      default: {
+        foo: '1.0.0',
+      },
+    },
+  })
+
+  expect(readYamlFile(filePath)).toStrictEqual({
+    packages: ['*'],
+    catalog: { foo: '1.0.0' },
+  })
+})
+
+test('updateWorkspaceManifest preserves quotes', async () => {
+  const dir = tempDir(false)
+  const filePath = path.join(dir, WORKSPACE_MANIFEST_FILENAME)
+
+  const manifest = `\
+catalog:
+  "bar": "2.0.0"
+  'foo': '1.0.0'
+  qar: 3.0.0
+`
+
+  const expected = `\
+catalog:
+  "bar": "2.0.0"
+  'foo': '1.0.0'
+  qar: 3.0.0
+  zoo: 4.0.0
+`
+
+  fs.writeFileSync(filePath, manifest)
+
+  await updateWorkspaceManifest(dir, {
+    updatedCatalogs: {
+      default: {
+        foo: '1.0.0',
+        bar: '2.0.0',
+        qar: '3.0.0',
+        zoo: '4.0.0',
+      },
+    },
+  })
+
+  expect(fs.readFileSync(filePath).toString()).toStrictEqual(expected)
+})