A mixed methods approach was applied to examine the effects of a naturally occurring teamwork intervention supported with training. The first objective was to integrate qualitative process evaluation and quantitative effect evaluation to examine how and why the training influence intervention outcomes. The intervention (N = 328) was supplemented with four training conditions (no training, team member training, team leader training, and a combination of training types). The second objective was to examine whether different training conditions support team member training in isolation, but not in combination, led to positive outcomes. The integrated analysis of qualitative and quantitative data indicated that a number of contextual factors interacted with training experiences and outcomes to influence the success of team intervention.