Although the vulnerabilities stemming from the intersection of aging and migration are widely recognized, the migration contexts and the factors influencing the mental health of older unforced migrants have received scant attention. This review explores the drivers of unforced migrations in later life and the individual, relational, and structural factors influencing their mental health and well-being. Following the Preferred Reporting Items for Systematic Reviews and Meta-Analyses guidelines, a systematic search of 7 databases for English peer-reviewed journal articles was conducted. A total of 21 studies were identified and analyzed inductively. The review classified motivations for migration as push factors and pull factors: push factors such as escaping structural inequities in the homeland and pull factors included seeking better lifestyle opportunities and reuniting with family. The positive determinants of mental health included cordial family relationships, paid employment, the presence of a partner, and strong support networks. Advanced age, absence of a partner, lifestyle changes, lack of intergenerational support, poor language proficiency, unfavorable policies, lack of access to resources, and systemic biases negatively affected the mental health of older unforced migrants. The review highlights the need to recognize the diversity among older migrants to develop policies and programs that address their specific circumstances. Recognizing their strengths, rather than focusing solely on their vulnerabilities will help create a more positive and supportive environment, enabling them to thrive in their new communities.