As the population ages, promoting an active and healthy lifestyle among older adults becomes increasingly crucial. This study investigates the role of psychological needs satisfaction in sustaining physical activity (PA) among seniors on Terceira Island, Azores. Seventy-eight participants, aged 50 to 80, from ten parishes engaged in a multicomponent PA program offered by the Azores Municipal Council. Data collected included functional physical fitness, overall health assessment, psychological needs for exercise, extrinsic motivation, behavioral regulation, and health-related quality of life. The findings indicate that older adults participating in PA three or more times per week exhibit higher motivation and greater satisfaction of psychological needs related to exercise. Promoting PA not only contributes to better health outcomes but also underscores the importance of creating supportive environments for exercise. This study’s results align with the United Nations Sustainable Development Goals, specifically SDG 3—Good Health and Well-Being, and SDG 11—Sustainable Cities and Communities. In summary, understanding how psychological needs impact PA sustainability is vital for developing effective strategies to enhance older adults’ well-being and supports global sustainability objectives.