We examined the extent to which member ability and personality relate to differences in team performance and team efficacy in a task setting that simulated the high degree of role interdependence and human-technology interaction found in many military contexts. 168 male participants were assigned to dyadic teams and trained for two weeks to learn and perform a complex computer task that simulated the demands of a dynamic aviation environment. Participants also completed measures of general mental ability, psychomotor ability, and the Big Five personality traits (extraversion, openness, conscientiousness, agreeableness, and emotional stability). Team performance and team efficacy were assessed multiple times throughout training. Results indicated that ability was a critical determinant of both performance and efficacy, and personality traits yielded an incremental contribution to both performance and efficacy. In particular, psychomotor ability and conscientiousness were the strongest and most consistent factors associated with team effectiveness.