This study, funded by the USC CTSI Voucher Program, examined the within-day effects of fathers’ parenting practices on children’s subsequent eating, physical activity, and sedentary behaviors. We recruited approximately 50 fathers whose spouses and 11 to 15-year-old children were current participants in the Mothers’ and Their Children’s Health (MATCH) study. Fathers completed one 7-day assessment which will include Ecological Momentary Assessment (EMA) sampling of parenting practices, accelerometry, and cortisol testing. The results from this study will inform development of a future parent-based child obesity prevention intervention using just-in-time smartphone-based intervention methodology to address parenting practices.