This study aimed to evaluate the effectiveness of the VAMOS strategy (Health-Improving Active Life) in improving physical activity (PA), dietary habits, and anthropometric variables of primary health care (PHC) users in Brazil. A randomized controlled community trial was conducted at two units of the Health Academy Program (HAP; a service provided by PHC), which were randomly assigned either to control group (CG) or intervention group (IG). Participants in both groups (CG = 156 and IG = 135) took part in physical activity classes provided by HAP facilities with those in IG also participating in the VAMOS strategy for 12 weeks. This strategy is based on social cognitive theory. The main behavioral constructs addressed were self-efficacy, goal setting, self-monitoring, identification of social support and barriers, and solutions for the identified barriers. Physical activity was measured with accelerometers, and nutritional status was assessed using dietary habits questionnaires and anthropometric measurements. Intention-to-treat analysis revealed that participants in IG increased the daily time of moderate-vigorous PA and the frequency of raw vegetable intake, while the intake of ultra-processed foods was reduced. Weight loss among participants who were classified as overweight/obese at baseline was observed in the intervention group compared to control. These results suggest that the VAMOS strategy was effective in increasing PA, healthy dietary habits, and decreasing weight among PHC users. Therefore, VAMOS could be used as a strategy to strengthen individuals' autonomy regarding healthy choices and improve their overall health.