Most jobs require teamwork. Are some people good team players? In this paper we design and test a new method for identifying individual contributions to group performance. We randomly assign people to multiple teams and predict team performance based on previously assessed individual skills. Some people consistently cause their group to exceed its predicted performance. We call these individuals “team players”. Team players score significantly higher on a well-established measure of social intelligence, but do not differ across a variety of other dimensions, including IQ, personality, education and gender. Social skills – defined as a single latent factor that combines social intelligence scores with the team player effect – improve group performance about as much as IQ. We find suggestive evidence that team players increase effort among teammates.