Studies highlight the importance of physical activity (PA) in relation to positive psychological functioning (PPF) among adults. Physical inactivity is strongly associated with lower levels of PPF, supporting the idea that lifestyle choices can be identified as a public health concern. There is growing evidence of the health benefits of regular PA. This study aims to analyze the contribution of PA to flow, PPF, and well-being. The sample consisted of 226 adults aged between 18 and 65 years (M = 41.23; SD = 12.50), mostly female (70.35%), with 56% reporting regular PA. Results revealed significant differences favoring active individuals over sedentary participants in all dimensions of flow, except for loss of self-consciousness. Regular PA was associated with higher levels of flow and psychological well-being. Both regular and intensive PA, as well as environmental mastery (EM), were key contributors to flow experiences, while self-acceptance and EM were central contributors to the Live Well Index. These findings support the association between PA and lower likelihood of sedentary lifestyles, emphasize its benefits for well-being, and highlight the association between PPF and active lifestyle patterns.