BACKGROUND: Despite the well-documented health benefits of Physical Activity (PA), older adults often struggle to engage in PA. The present review examines the relationship between PA, motivation and basic psychological needs among older adults aged 65 and over, through the lens of Self-Determination Theory (SDT). METHODS: Relevant studies that used qualitative methodologies and applied SDT framework were systematically searched in five electronic databases (i.e. Scopus, Web of Science, PubMed, PsycINFO and CINAHL). Methodological rigour was assessed using the GRADE-CERQual (Confidence in the Evidence from Reviews of Qualitative Research). RESULTS: 21 studies met inclusion criteria (N = 412; ages 65-97). Four themes and nine subthemes were identified. Peer relationships emerged as a pivotal element in supporting most autonomous forms of motivation and satisfying psychological needs (i.e. autonomy, competence and relatedness). A peer coach was preferred during several health programs, enhancing competence and relatedness. Outdoor activities in natural settings promoted intrinsic motivation, while indoor activities were driven more by extrinsic motivation. Barriers included ageist stereotypes and perceptions of inevitable physical decline, which negatively impacted competence and autonomy, ultimately reducing motivation for PA. CONCLUSIONS: This qualitative synthesis highlights a complex interplay of SDT components and social factors in influencing PA behaviours among older adults. Tailored interventions that integrate social interaction, provide feedback from coaches and offer choices among several exercises with graduate intensity levels are likely to enhance adherence in PA. Future interventions should address both psychological and social barriers to create inclusive PA strategies that meet older adults' needs and motivation.