diff --git a/.changeset/healthy-lions-judge.md b/.changeset/healthy-lions-judge.md
new file mode 100644
index 0000000000..f9ead85d2e
--- /dev/null
+++ b/.changeset/healthy-lions-judge.md
@@ -0,0 +1,6 @@
+---
+'@backstage/plugin-auth-backend-module-aws-alb-provider': minor
+'@backstage/plugin-auth-backend': minor
+---
+
+**BREAKING**: The AWS ALB `fullProfile` will no longer have the its username or email converted to lowercase. This is to ensure unique handling of the users. You may need to update and configure a custom sign-in resolver or profile transform as a result.
diff --git a/plugins/auth-backend-module-aws-alb-provider/src/authenticator.ts b/plugins/auth-backend-module-aws-alb-provider/src/authenticator.ts
index 2e7fe1cd26..b6969c5432 100644
--- a/plugins/auth-backend-module-aws-alb-provider/src/authenticator.ts
+++ b/plugins/auth-backend-module-aws-alb-provider/src/authenticator.ts
@@ -77,12 +77,12 @@ export const awsAlbAuthenticator = createProxyAuthenticator({
         provider: 'unknown',
         id: claims.sub,
         displayName: claims.name,
-        username: claims.email.split('@')[0].toLowerCase(),
+        username: claims.email.split('@')[0],
         name: {
           familyName: claims.family_name,
           givenName: claims.given_name,
         },
-        emails: [{ value: claims.email.toLowerCase() }],
+        emails: [{ value: claims.email }],
         photos: [{ value: claims.picture }],
       };