Your lender will conduct a hard credit check when you apply for a HELOC, which can cause a slight, temporary decrease in your credit score. This type of credit check typically stays on your credit reports for two years, though it might only impact your credit score for up to a year. Apart from that, the way you use and repay your HELOC could impact your score. Borrowing against a HELOC can increase your credit utilization ratio, which factors into your credit score. A higher credit utilization ratio could result in a lower credit score. That said, paying down your HELOC over time could help you build credit.