diff --git a/.changeset/late-turtles-sparkle.md b/.changeset/late-turtles-sparkle.md
new file mode 100644
index 0000000000..f0b28cdb87
--- /dev/null
+++ b/.changeset/late-turtles-sparkle.md
@@ -0,0 +1,5 @@
+---
+'@backstage/plugin-auth-backend': patch
+---
+
+Declare oauth2 `clientSecret` with visibility secret
diff --git a/plugins/auth-backend/config.d.ts b/plugins/auth-backend/config.d.ts
index 791bd3606b..af5a3c24be 100644
--- a/plugins/auth-backend/config.d.ts
+++ b/plugins/auth-backend/config.d.ts
@@ -90,6 +90,9 @@ export interface Config {
       oauth2?: {
         [authEnv: string]: {
           clientId: string;
+          /**
+           * @visibility secret
+           */
           clientSecret: string;
           authorizationUrl: string;
           tokenUrl: string;