Our decision about whether to trust and cooperate with someone is influenced by the individual's facial appearance despite its limited predictive power. Thus, remembering trustworthy-looking cheaters is more important than remembering untrustworthy-looking cheaters because we are more likely to trust and cooperate with the former, resulting in a higher risk of unreciprocated cooperation. The present study investigated whether our mind adaptively copes with this problem by enhancing memory for trustworthy-looking cheaters. Participants played a debt game, wherein they learned to discriminate among good, neutral, and bad lenders, who respectively charged no, moderate, and high interest on the debt. Each lender had either a trustworthy- or untrustworthy-looking face. A subsequent memory test revealed that participants remembered the bad traits of trustworthy-looking lenders more accurately than those of untrustworthy-looking lenders. The results demonstrate enhanced memory for trustworthy-looking cheaters, or wolves in sheep's clothing, implying that humans are equipped with protective mechanisms against disguised, unfaithful signs of trustworthiness. (Contains 1 table and 2 figures.)