Background <p>Motivation and self-efficacy are well-established predictors of engagement and persistence within structured exercise programmes. Yet it remains unclear whether these psychological factors predict objective adherence metrics and associated fitness outcomes within home-based exercise programmes for older adults.</p> Methods <p>This study adopted a person-centred approach to examine whether distinct psychological profiles predict objective adherence and fitness outcomes following a 26-week home-based exercise programme in 88 older adults (age = 67.2 ± 5.5 years). Objective adherence was defined as compliance with the prescribed exercise volume and quantified using cumulative metabolic equivalent minutes (MET-mins) derived from heart rate data reflecting session intensity and duration across the programme, as opposed to behavioural self-report measures. Psychological profiles were generated using latent profile analysis based on autonomous motivation, controlled motivation, and exercise self-efficacy.</p> Results <p>Two profiles were identified: an autonomous and highly confident profile characterised by high self-efficacy and autonomous motivation, and a moderately autonomous and confident profile characterised by lower self-efficacy and autonomous motivation. Controlled motivation was similar between groups. Profiles did not differ in demographic or physiological characteristics at baseline. Adherence was high and comparable across the two profiles for all indices (e.g., cumulative MET-mins: 129 ± 66% vs. 116 ± 38%). Furthermore, both profiles demonstrated significant and comparable improvements in cardiorespiratory fitness (V̇O₂peak), handgrip strength, flexibility (chair sit-and-reach; back scratch), and mobility (8-foot up-and-go). </p> Conclusions <p>Baseline differences in self-efficacy and autonomous motivation among older adults did not significantly predict adherence or fitness outcomes within a structured, well-supported home-based exercise programme. The programme incorporated consistent objective monitoring of exercise behaviour, along with regular guidance and feedback from the research team delivered through scheduled participant contact. This level of structured behavioural support may have reduced the influence of psychological profile membership on exercise adherence and fitness outcomes, resulting in comparable positive outcomes across participants. Future research should investigate whether motivation profiles become more predictive of long-term adherence and sustained fitness outcomes once external behavioural support is reduced or withdrawn.</p> Trial registration <p>Open Science Framework: <a href="https://osf.io/6fqg7">https://osf.io/6fqg7</a></p>