The authors demarcated mental efficacy and physical efficacy at the team level, and they explored these 2 factors as outcomes of 4 potential inputs and as predictors of 3 outcomes among 110 newly formed action teams in a military setting. Both types of team efficacy benefited from greater team size and an initial experience of enactive mastery, but they were not influenced by teams' female representation or knowledge pool. In terms of predictive contributions, both mental and physical efficacy facilitated internal social cohesion, yet only mental efficacy promoted problem solving and observed teamwork effectiveness.