Background. Herpesviruses have been linked to cognitive impairment in older individuals but little is known about the association in the general US population. Methods. We determined whether cytomegalovirus (CMV) and herpes simplex virus 1 (HSV-1) seropositivity were associated with cognitive impairment among children (aged 6-16 years) and adults aged 20-59 or ≥60 years, using data from the National Health and Nutrition Examination Survey (NHANES) III. Linear and logistic regression models were used to examine the associations between pathogen seropositivity and cognitive impairment. Results. Among children, HSV-1 seropositivity was associated with lower reading and spatial reasoning test scores (β, -0.69; 95% confidence interval CI, -1.18 to -.21 and β, -0.82; 95% CI, -1.29 to -.36, respectively). Among middle-aged adults, HSV-1 and CMV seropositivity were associated with impaired coding speed (odds ratio OR, 1.54; 95% CI, 1.13-2.11, and OR, 1.41; 95% CI, 1.09-1.82, respectively). CMV seropositivity was also associated with impaired learning and recall (OR, 1.43; 95% CI, 1.14-1.80). Among older adults, HSV-1 seropositivity was associated with immediate memory impairment (OR, 3.26; 95% CI, 1.68-6.32). Conclusions. Future studies examining the biological pathways by which herpesviruses influence cognitive impairment across the life course are warranted.