There are pros and cons to accepting a credit limit increase, but generally, accepting a credit limit increase will improve your credit score.
Typically, your credit is increased in one of two ways, the first is an automatic increase, and the second is one where the lender tells you that you "may" be eligible for an increase.
Accepting a credit limit increase can help your credit score by lowering your credit utilization: your credit utilization is used to calculate your credit score. By increasing your limit, you have more funds available; if you keep your outstanding down with a higher limit, you could improve your score
One of the disadvantages of increasing your credit limit is that it may come with hard inquiries. If you get a letter or an offer from the bank saying you "may" be eligible for an increase, you should ask if it comes with a hard inquiry as this may affect your credit score negatively.