Background <p>The transition from working life to retirement represents a life-course transition that can influence mental health of older adults. While retirement may provide opportunities for autonomy, leisure and personal development, it may also increase vulnerability to depression, loneliness, social isolation and loss of purpose. This scoping review aimed to identify and synthesize protective and risk factors that influence mental health during the transition to retirement.</p> Methods <p>We conducted a scoping literature review following the PRISMA-ScR (Preferred Reporting Items for Systematic Reviews and Meta-Analyses extension for Scoping Reviews) guidelines and PRISMA-S checklist for literature search. PubMed, APA PsycINFO, CINAHL and Web of Science were searched for peer-reviewed studies published between 2015 and 2026. Studies focusing on adults aged 50 years and older that addressed factors influencing mental health during the transition from work to retirement were included. Data extraction was followed by thematic analysis and narrative synthesis to identify recurring themes, protective and risk factors.</p> Results <p>Twenty seven studies were included in the review. Depression and depressive symptoms were the most frequently investigated mental health outcomes. The identified factors were grouped into socioeconomic, health-related, psychosocial, employment-related and retirement-related domains. Protective factors included financial security, good health, voluntary and planned retirement, social participation, volunteering, post-retirement employment, social relationships, optimism and maintenance of purpose and identity. Risk factors included involuntary or poorly planned retirement, financial insecurity, chronic illness, loneliness, social isolation, unemployment, loss of work-related identity and reduced perceived control over retirement. Across studies, maintaining control, social connectedness and meaningful engagement emerged as key determinants of positive mental health outcomes.</p> Conclusions <p>Mental health during the retirement transition is influenced by interacting socioeconomic, health-related, psychosocial and retirement-related factors. The findings highlight the importance of financial stability, social participation, autonomy, health and meaningful engagement in supporting mental wellbeing. The existing evidence base remains fragmented, only partially grounded in theoretical frameworks and it lacks evidence on how digital health interventions can support the transition to retirement. This highlights an important gap in the literature and the need for future intervention-oriented research.</p>