Under the mandate of the Dodd-Frank Wall Street Reform and Consumer Protection Act of 2010, the SEC is soliciting public opinions on whether broker-dealers should be subject to a fiduciary duty when advising retail and institutional investors. This Article focuses on the advisability of such a proposal for institutional investors. It shows that, first, a fiduciary duty could potentially enhance broker-dealers’ standard of conduct for only a subset of institutional investors who are well capitalized, capable of assessing risks independently, and acknowledge in writing their nonreliance on broker-dealers’ advice. Thus, the benefit of fiduciary duty is much narrower than what its proponents believe. Second, institutional investors face substantial obstacles in recovering damages from brokerdealers who violate their standard of conduct in private litigation, and yet fiduciary duty would not help in this regard. In light of fiduciary duty’s negligible benefit but indeterminate cost to the financial industry, it is not a viable measure for enhancing institutional investor protection.