While a great deal of research has examined students' critical thinking skills, less is known about students' tendencies to use these skills. Specifically, little is known about what factors contribute to students developing a disposition to think critically or what impact this disposition has on college students' academic achievement. Perceived control, which has been found to be an important factor in college students' academic success, may be an important factor in developing this disposition. The current longitudinal study examined the reciprocal-effects between critical thinking disposition and perceived academic control, and their comparative influences on academic achievement in 1196 first-year college students. Using a two-wave, two-variable cross-lag structural equation model, a reciprocal-effect was found whereby students' perceived academic control predicted their subsequent critical thinking disposition, and students' critical thinking disposition predicted their subsequent perceived academic control. Furthermore, after controlling for high school academic performance, perceived academic control was found to have a stronger impact on students' GPAs than critical thinking disposition. Implications of fostering a critical thinking disposition and perceived academic control among college students are discussed.