This study investigates associations between two types of control beliefs--self-efficacy for self-regulation and implicit theories of willpower--and undergraduate biology students' (N = 535) behavioral self-regulation and performance. Findings suggest that self-efficacy is the more proximally related motive for students to engage in academic self-regulatory behaviors, as it was directly related to both behavioral self-regulation and course grades. In contrast, implicit theories about willpower were indirectly associated with both outcomes through self-efficacy. Collectively, results support implicit theories about willpower as a potential influence on how students interpret mental effort, in turn raising or lowering self-efficacy, ultimately predicting their self-regulatory behaviors and grades. Theoretical and practical implications are discussed.