The first year of college presents numerous challenges experienced as overwhelming by some freshmen who may become overly stressed and depressed. This longitudinal study examined perceived academic control (PAC) as a mediator of optimism and social support's buffering effects on freshman students' psychological health. Multiple regressions assessed optimism and social support (at the start of the academic year) as predictors of year-end stress and depression among 288 freshmen. PAC (at the start of the year) was then examined as a mediator of the effects of optimism and support. Lastly, stress and depression were assessed as predictors of year-end degree commitment and cumulative GPA. As expected, optimism and support predicted less stress and depression, yet their beneficial effects were mediated by students' PAC. Depression subsequently predicted less year-end degree commitment and lower cumulative GPAs. PAC mediates the protective effects of optimism and support, providing additional protection for students against poor psychological health. Findings have implications for shielding students' health against the demands of the freshman year.