Initially, depending on your cosigner’s or co-borrower’s overall credit picture, the loan might increase their overall debt-to-income ratio, which is one factor credit bureau’s use to determine a credit score. However, as long as you make your monthly payment on time and pay off your loan by the end of the term and don’t take on any new debt, it shouldn’t hurt your cosigner’s or co-borrower’s credit score in the long run. If you don’t make timely payments, it could hurt their credit score.