Parents play a critical role in supporting their children's physical activity (PA) and sedentary behavior (SB). However, less is known about parents' support for child PA and SB in underserved populations. In this study, we examined the associations between parent and child total PA (TPA), SB, and moderators of these associations in a primarily Hispanic/Latino sample. This cross-sectional study used baseline data from 68 parent-child dyads who participated in a two-group randomized controlled trial. TPA and SB were measured for seven consecutive days using GeneActiv wrist-worn accelerometers. Multivariable linear regression was used to evaluate the parent-child TPA and SB associations [betas (ß) and 95% confidence intervals (CIs)]. We examined child sex (girl versus boy), child age (6-10 versus 11-12 years), and day of week (weekday versus weekend) as moderators of these associations. In covariate-adjusted models, there were no statistically significant associations between parent-child TPA (ß = - 0.04, 95%CI = - 0.20, 0.13) or SB (ß = 0.05, 95%CI = - 0.13, 0.22), and child sex and child age did not modify these associations (P