Background: Latinos in the United States face multiple barriers to engaging in physical activity (PA). We implemented a faith-based multilevel intervention to promote PA in parks for Latino adults, which was partially adapted to a virtual platform during the COVID-19 pandemic, and evaluated it using the Reach, Effectiveness, Adoption, Implementation, and Maintenance framework. Methods: We conducted in-depth semistructured interviews (83% in Spanish) with 24 intervention participants (75% women) participating in a cluster randomized controlled trial in 2019–2022 that linked 6 churches (3 intervention, 3 control) with parks in East Los Angeles, CA. The intervention included in-person, park-based fitness classes, which were adapted to Facebook during the pandemic; PA motivational text messages; and other activities. Interviews assessed Reach (participation), Effectiveness (perceived impacts), Implementation (participation barriers/facilitators), and Maintenance (plans for sustaining PA), as well as perceived pandemic impacts. Results: About 80% of interviewees participated in ≥1 park class and 67% in ≥1 virtual class (Reach). Interviewees perceived positive intervention impacts across multiple health and well-being domains (Effectiveness) despite perceived negative pandemic impacts; several facilitators to participation (personal, social, program) and few barriers (personal, virtual, environmental; Implementation); and plans for maintaining PA (eg, revisiting intervention text messages and video recordings; Maintenance). Conclusions: Findings support the utility of Reach, Effectiveness, Adoption, Implementation, and Maintenance to understand the broad impacts of a faith-based PA intervention. Findings point to the adaptability and robustness of the intervention during a public health crisis. Overall, findings may help inform the translation of the intervention to other communities to advance health equity.