I signed up with Pokemon GO back when it first came out using my Gmail account rather than a trainer account. However, I do also have a Pokemon Trainer Club account that shares a username with my Pokemon Go account and also is tied to the same email I used to create my Pokemon GO profile.
When I log in to Pokemon GO, it shows my username (the same username that my Trainer Club account uses) and that it's linked to my Gmail address. Yet when I log in using the Trainer Club option, it's an entirely separate account.
Why does this happen and is there a way to be able to log in using either my Trainer Club account or my Gmail address to log in to the same account (since both accounts have the same username & same email tied to them)?
Best Answer
Just because the username of your Pokemon Trainer Club account is identical to that of your Gmail doesn't mean that they are the same account.
Your Gmail account took the name that is the name of your Trainer Club account but not the Trainer Club's PoGo-related account.
If you were to set up an account on PoGo with your Trainer Club account, you would need to give it a different username in PoGo to your Gmail account (since your Gmail account has reserved that name).
You cannot log into the same account with both your Gmail and Trainer Club - they can only log into separate accounts. You can, however, log into the same Gmail account with Facebook.
Also of note, having multiple accounts is a violation of Niantic's term of service. Using both a Gmail PoGo account and a Trainer Club PoGo account would violate this.