Background: There is evidence that physical activity (PA), sitting time, and obesity may impact cognition, but few studies have examined this in young women. Methods: Healthy women (18-35 y), without conditions that impair cognition, were recruited for this cross-sectional study. Participants completed anthropometric and validated computerized cognitive assessments (IntegNeuro™). Performance on 5 cognitive domains (impulsivity, attention, information processing, memory, and executive function) was reported as z scores. Sitting hours and weekly PA calculated from time in low-, moderate-, and high-intensity activity were obtained via the International Physical Activity Questionnaire. Analysis of variance/analysis of covariance, chi-square, and linear regression were used. Results: 299 (25.9 [5.1] y) women (low PA = 19%; moderate PA = 40%; high PA = 41%) participated. High PA women had lower body mass index (high PA = 26.1 [6.5]; moderate PA = 30.0 [8.7]; low PA = 31.0 [11.1] kg/m2; P <.001) and less sitting time (high PA = 6.6 [3.1]; moderate PA = 7.7 [2.8]; low PA = 9.3 [3.6] hr/weekday; P <.0001). Cognitive function was within normal ranges and did not differ between any PA groups (P =.42). Adjusting for body mass index, C-reactive protein, or sitting hours did not alter results. Weak correlations were found between time in high-intensity activity and impulsivity (b = 0.12, r2 =.015; P =.04), and between sitting hours and information processing efficiency (b = −0.18, r2 =.03; P =.002). Valuesare presented as mean (SD). Conclusions: Cognitive function was within the normal range, regardless of PA or sitting time.