Sex differences in a variety of psychological characteristics are well-documented, with substantial research focused on factors that affect their magnitude and causes. Particular attention has focused on mental rotation, a measure of spatial cognition, and on activity interests. We studied whether sex differences in visual perception—luminance contrast thresholds and motion duration thresholds—contribute to sex differences in mental rotation and interest in male-typed activities. We confirmed sex differences in vision, mental rotation, and activity interests in a sample of 132 college students. In novel findings, we showed that vision correlated with mental rotation performance in women, that vision was a better predictor of individual differences in mental rotation than sex, and that contrast thresholds correlated with women’s interest in male-typed activities. These results suggest that sex differences in spatial cognition and activity interests may have their roots in basic perceptual processes.