Promotoras from the communities in which interventions are implemented can be effective contributors to validity and fidelity efforts. This article describes a 48-week randomized controlled trial Madres para la Salud (Mothers for Health) and illustrates the use of promotoras as collaborative members of the research team to contribute to attaining integrative validity and treatment fidelity. Madres para la Salud implements a culturally tailored physical activity program to effect changes in body fat, systemic and fat tissue inflammation, and depression symptoms. The significance of Madres para la Salud treatment validity and fidelity processes includes cultural tailoring of a social support intervention, and a promotora model to incorporate initial and ongoing fidelity monitoring.