Loneliness and social isolation are increasingly recognized as major public health challenges, particularly among older adults. This review aims to identify and map the key risk and protective factors associated with loneliness and social isolation, with particular emphasis on the role of employment and work activity in later life. In accordance with Preferred Reporting Items for Systematic Reviews and Meta-Analyses extension for Scoping Reviews (PRISMA-ScR) guidelines, peer-reviewed studies published in 2019–2025 in the PubMed and Scopus databases were analyzed. The results showed that health-related, psychological, sociocultural, and socio-environmental factors are closely associated with the experience of loneliness in old age. The most numerous were health-related and sociocultural factors. Employment and social engagement played a particularly important role in mitigating loneliness by providing structure, purpose, and social contact. The transition from work to retirement was identified as a critical life stage that can either intensify or alleviate loneliness, depending on individual circumstances and the cultural context. Future research should adopt a longitudinal and cross-cultural approach to better understand how the moment of retirement affects loneliness in the long term. There is also a need to explore gender and socioeconomic differences in how older adults experience and cope with social isolation. Moreover, evaluating the effectiveness of workplace and community-based interventions aimed at fostering social connectedness after retirement could provide valuable evidence for developing public health strategies that support healthy and active ageing. Int J Occup Med Environ Health. 2025;38(6)