The cognitive influences of omega-3 polyunsaturated fatty acids (n-3 PUFA) remain unclear throughout the life span. Dietary n-3 PUFA appear cognitively beneficial prenatally and neuroprotective at later age; however, researchers using supplementation designs have reported disparate findings across age groups. Few studies have examined the cognitive impact of n-3 PUFA during young adulthood. This study assessed the cognitive effects of fish oil supplementation at college age, hypothesizing benefits on affect, executive control, inhibition, and verbal learning and memory. College-aged participants were assigned to active (n = 20, 5 men; age = 19.9, sage = 1.8) or placebo (n = 21, 7 men; age = 20.4, sage = 1.6) treatments, receiving fish oil (480 mg DHA/720 mg EPA) or coconut oil, respectively. Both groups completed four weeks of supplementation. At baseline and posttreatment, the researchers administered the Rey Auditory Verbal Learning Test (RAVLT; Lezak, 1995), Stroop Color and Word Test (SCWT; Golden & Freshwater, 2002), Trail Making Test (TMT; Corrigan & Hinkeldey, 1987; Gaudino, Geisler, & Squires, 1995; Lezak, 1995), and Positive and Negative Affect Schedule (PANAS; Watson, Clark, & Tellegen, 1988). Repeated-measures ANOVAs indicated no benefits of fish oil on the SCWT, RAVLT Stages 1 to 5, or PANAS. An interaction occurred between condition and time of measurement (i.e., baseline and posttreatment) on RAVLT Stages 6 and 7, and placebo significantly improved TMT performance over fish oil. The benefits of n-3 PUFA on RAVLT performance derived more from depreciated placebo performance than improved performance due to fish oil. The placebo gain on TMT performance likely derived from a learning effect. Together, these results present limited cognitive benefits of n-3 PUFA at college age; however, the treatment may have been subtherapeutic, with a larger sample needed to generalize these results.