Mexican-heritage children often achieve less physical activity (PA) than their counterparts and are at greater risk for associated comorbidities. Child PA is greatly influenced by their parents, yet researchers have rarely involved fathers in community health promotion. The purpose of this study is to examine Mexican-heritage fathers’ perceptions of responsibilities and self-reported activities. Promotoras recruited fathers (n = 300) from colonies on the Texas–Mexico border and administered Spanish-language surveys including paternal responsibilities, father PA, and PA co-participation. Two researchers coded responses. Open-ended items were coded and cross-tabulations between responsibilities and activities with children were examined. Fathers reported feeling monetary responsibilities most often. Fathers reported engaging in more activities with their sons than daughters; however, fathers engaged in very few activities specifically with their children. Feeling responsible for family expenses was associated with paternal PA co-participation with family and children. This study adds clarity to the role of Mexican-heritage fathers in child PA. Findings highlight potential areas for intervention including supporting fathers to take an active role in their children’s PA.