Cognitive performance has been extensively investigated in relation to insomnia, yet review of the literature reveals discrepant findings. The current study aimed to synthesize this literature with a systematic review and meta-analysis. 48 studies (k = 50 independent samples, n = 4539 total participants) met inclusion criteria. Omnibus meta-analysis revealed insomnia was associated with poorer overall cognitive performance (Hedge's g = −0.24, p < 0.001). Analyses by cognitive domain revealed insomnia was specifically associated with impairments in subjective cognitive performance (g = −0.35), and objective measures of perceptual function (g = −0.24), manipulation (g = −0.52) and retention/capacity in working memory (g = −0.30), complex attention (g = −0.36), alertness (g = −0.14), episodic memory (g = −0.29), and problem solving in executive functions (g = −0.39). Age, percent female, publication year, and insomnia measure did not consistently moderate findings. Approximately 44% of studies failed to use diagnostic criteria when categorizing insomnia and cognitive measures varied widely. This indicates a need for standardization of methods assessing insomnia and cognitive performance in research. Overall, findings from this meta-analysis indicate insomnia is associated with impairment in objective and subjective cognitive performance, highlighting the utility of treating insomnia to potentially improve cognitive outcomes.