The interest rate on your credit card doesn't affect your credit score, but opening a new credit card account can temporarily lower your score. And remember, if you run up a high balance because you have a low introductory interest rate, you may increase your credit utilization ratio and hurt your credit score. However, opening a new account and keeping the balance low can improve your credit score, so once you pay off the purchases your make on your new account, your credit score may go up.