This article explores the implications of a negotiator setting high aspirations on the counterpart's assessments of the negotiator and future cooperation toward the negotiator. Participants were 134 undergraduates acting as buyers or sellers in a single-issue price negotiation. Buyers received instructions to set more or less ambitious aspirations. Buyers who set more ambitious aspirations achieved better economic outcomes. However, sellers paired with buyers setting more ambitious aspirations found their buyers to be less likeable, expressed less willingness to cooperate with them in the future, and behaved less generously toward them in a postnegotiation dictator game. The perceived likeability of the buyer explained why the sellers were less willing to cooperate in the future with buyers who had set more ambitious aspirations. This research contributes to the understanding of the downside of setting high aspirations in a competitive negotiation and provides implications on balancing one-time economic gain with future social loss.