How do I delete a credit card I no longer own?

Is the credit card your only account for this bank?

If so and you no longer wish to keep any transaction history for the account, simply delete the account from Mint. 

Please note that completely deleting an account will delete all the data history in Mint. 

Is the credit card one sub-account out of multiple accounts in your bank OR Is the credit card is old and you received a new card?

If one of these is the case, you can close the account so you will no longer see any balance for it. Closed accounts maintain the transaction history in Mint. 

You can also hide the account if you don't want to see the transaction history. 

For more information about closing and hiding accounts, please click here.