This paper looks at the role of both commercial and investment banks in providing merger advisory services. In this area, unlike some areas of investment banking, commercial banks have always been allowed to compete directly with investment banks. In their dual role as lenders and advisors to firms that are the target or the acquirer in a merger, banks can be viewed as serving a certification function. However, banks acting as both lenders and advisors face a potential conflict of interest that may mitigate or offset any certification effect. Overall, we find evidence supporting the certification effect for target firms. In contrast, conflicts of interest appear to dominate the certification effect when banks are advisors to acquirers.