Four studies explored behavioral forecasting and the effect of competitive expectations in the context of negotiations. Study 1 examined negotiators' forecasts of how they would behave when faced with a very competitive versus a less competitive opponent and found that negotiators believed they would become more competitive. Studies 2 and 3 examined actual behaviors during a negotiation and found that negotiators who expected a very competitive opponent actually became less competitive, as evidenced by setting lower, less aggressive reservation prices, making less demanding counteroffers, and ultimately agreeing to lower negotiated outcomes. Finally, Study 4 provided a direct test of the disconnection between negotiators' forecasts for their behavior and their actual behaviors within the same sample and found systematic errors in behavioral forecasting as well as evidence for the self-fulfilling effects of possessing a competitive expectation.