Due to the expanding aging population, Masters sport is becoming an increasingly popular activity for older adults (Weir et al., 2010). However, few resources are available to support lifelong sport adherence for middle-aged and older adults in competitive sport, or Masters athletes (MAs). The purpose of the thesis was to explore how MAs apply deliberate psychological strategies as a support to enhance their performance, experience, or adherence to the adult sport lifestyle. It also explored how mental performance consultants (MPCs) viewed the application of sport psychology to MAs, including content to which skills/strategies could be applied, and delivery approaches. In Manuscript 1, semi-structured interviews were conducted with eight Canadian MAs (Mage = 51, range 38-62; 3 males, 5 females) from 12 sports (10 individual, 2 team) to explore how they applied psychological skills/strategies as a support to the Masters sport experience. Data were thematically analyzed (Braun & Clark, 2012) deductively (Weinberg & Gould, 2015) and inductively. The results demonstrated that MAs used traditional mental skills predominantly to enhance performance, while novel Masters-specific skills were used to maintain sport adherence. MAs promptly illustrated sport psychology content, but were rather limited when discussing their methods/techniques. In Manuscript 2, five two-person semi- structured group interviews were pursued with ten professional Canadian MPCs (8 women, 2 men) who had experience consulting MAs. These interviews explored the content consultants delivered to MAs and whether there were implications of specific adult attributes associated with service delivery. Data were thematically analyzed (Braun & Clark, 2012) inductively. The results showed MPCs’ perceptions on psychological content they believed was highly pertinent in their consulting practice with MAs. Specifically, they described targeted content related to performance readiness, prioritizing sport, protecting/recovering sport enjoyment, and aging/self-compassionate considerations. MPCs also highlighted nuances related to approaches to consultation with adult sportspersons and the delivery of psychological services to MAs. In both studies with the MAs and the MPCs, interviewees described various barriers and constraints that influenced approaches to consultation and service delivery. Altogether, the corroborative results from both studies suggest the benefits of psychological support services for MAs, the use of MPCs’ services and expertise as an additional support to maintain lifelong sport activity, and provide a formative guide for content and approaches to delivery with the Masters clientele.