This experiment examined the effects of motivational orientation (prosocial versus egoistic) on interpersonal trust, negotiation behavior, amount of impasses, and joint outcomes in three-person negotiations. Students participated in a joint venture negotiation, in which motivational orientation was manipulated by allocating individual incentives (egoistic motive) vs. team incentives (prosocial motive). Results indicated that prosocially motivated negotiators achieved more integrative agreements and fewer impasses, and reported higher trust, more problem solving, and less contending behavior than egoistically motivated negotiators. Hierarchical regression suggested that the finding that prosocial groups achieved higher joint outcomes can be explained by higher levels of trust, more problem solving behavior, and less contending behavior in prosocial groups.