Are happy people more likely to be cooperative and successful negotiators? On the basis of the Affect Infusion Model (AIM; Forgas, 1995a), Experiment 1 predicted and found that both good and bad moods had a significant mood-congruent effect on people's thoughts and plans, and on their negotiation strategies and outcomes in both interpersonal and intergroup bargaining. Experiment 2 replicated these results and also showed that mood effects were reduced for persons more likely to adopt motivated processing strategies (scoring high on machiavellianism and need for approval). Experiment 3 confirmed these effects and demonstrated that the mood of the opposition also produced more mood-congruent bargaining strategies and outcomes. The results are discussed in terms of affect priming influences on interpersonal behaviors, and the implications of these findings for real-life cognitive tasks and bargaining encounters are considered.