Previous research examining the link between insomnia and cognitive functioning is limited and mixed. The current study investigated this relationship using self-report in a large sample of college undergraduate students (N = 941; 65% female, mean age of 20 years). Regression analyses revealed that insomnia severity predicted cognitive failures overall, as well as on each of four subscales of cognitive failures: memory, distractibility, blunder, and memory for names. Hierarchical regression further showed that the relationship between insomnia severity and cognitive failures was significant even after controlling for possible confounding variables of depression, negative affect, stress, and anxiety. Additionally, it was found that insomnia partially mediated the relationship between cognitive failures and depression, negative affect, and trait anxiety. Future work in this area would benefit from adding a measure such as ecological momentary assessment to expand on these findings. Possible limitations, explanations, and implications of the present study and future direction are discussed.