The lack of environmental supports for healthy lifestyles is a potent factor in the high prevalence of noncommunicable diseases among communities experiencing economic disadvantage. Stronger Austin aimed to increase access to free physical activity (PA) and fitness programming (eg, Zumba) in underserved communities in Austin, Texas, via a partnership and interweaving into context approach in which classes are interwoven into settings with widespread access for residents, including clinics, city-supported housing, parks, recreation centers, and schools. We aimed to better understand the PA-related benefits and opportunities for improvement when adult fitness classes are interwoven into community settings. A mixed-methods design guided the study, which included SOFIT (Structured Observation of Fitness Instruction Time) assessments of class PA (n = 160 participants) and qualitative assessment of highlights and recommendations for class improvement via participant focus groups (n = 24), open-ended questionnaires (n = 258), and instructor interviews (n = 6). Findings indicated high levels of class PA (76.9%-86.9% of 1-hour class spent in moderate-to-vigorous PA; mean of 18 participants per class), with positive social connectedness cited as a key benefit. Challenges and best practices of community-based fitness classes are explored. Stronger Austin's partnership and interweaving into context approach represents a promising model for increasing access to fitness classes in underserved communities.