S&P revised its outlook to "negative" from "stable" on Goldman's "AA-minus" and Lehman's "A-plus" long-term credit ratings, suggesting a possible downgrade in one to two years.
The ratings are S&P's fourth- and fifth-highest investment grades, respectively. Lower credit ratings can result in higher borrowing costs.
Goldman is the largest Wall Street investment bank by market value, and Lehman is the fourth-largest. Goldman did not immediately return calls seeking comment. Lehman spokeswoman Kerrie Cohen declined to comment.
Banks have suffered from lower earnings and share prices as the housing crisis, a slowing economy and worries about credit quality led investors to stop buying a wide range of riskier securities. This has cut into revenue from trading, arranging debt offerings, and advising on mergers.