Two multisource studies address the interactive effects of personal and contextual variables on employees' proactive behavior. In line with previous work, we find positive main effects of transformational leadership, role breadth self-efficacy, and job autonomy on employee proactive behavior (personal initiative in Study 1 and prosocial proactive behavior in Study 2). As expected, a 3-way interaction qualifies these main effects: In situations of high autonomy, transformational leadership relates positively to proactive behavior for individuals high (but not low) on self-efficacy. Vice versa, in situations low on job autonomy, transformational leadership relates positively to proactive behavior for individuals low (but not high) on self-efficacy. This pattern is found both for self-ratings and peer-ratings of employees' proactive behavior in Study 1 and for supervisor ratings of such behavior in Study 2.