Physical activity (PA) is a public health priority due to holistic health benefits; however, many adults do not meet PA guidelines. Few studies have examined Mexican-heritage fathers’ social networks, specifically with whom they are physically active. This study examines changes in Mexican-heritage fathers’ PA networks after participation in a father-focused, family-centered health program. Families consisting of child (aged 9-11 years), mother, and father were recruited from colonias on the Texas-Mexico border for participation in a 6-week father-focused, family-centered program concentrated on healthy eating and active living. Fathers reported up to 5 people with whom they were active most in the previous month before and after the program as well as how often they were active with the person and what activities they did most often. Multilevel regression models examined changes in networks. Fathers (n = 42; mean age = 39.07 years, SD = 7.45) were significantly more likely to report more frequent PA with others after the program as compared with before. General active play and conditional support were mentioned most frequently. This study provides context to the social networks and PA behaviors of Mexican-heritage fathers and suggests that a father-focused, family-centered health program can increase the PA frequency with social network connections.