Despite the numerous challenges of ageing in a foreign land, many older immigrants are fairly resilient and report experiencing good wellbeing. The key question that the present paper addresses is how this is achieved. Drawing on frameworks from cross-cultural and social identity literatures, the present study proposes and tests a model of serial multiple mediation that identifies possible mechanisms supporting the wellbeing of older immigrants who have resided in the host country for some time. In this model, it is predicted that new group memberships acquired post-migration enable access to social support that in turn provides the basis for perceived integration, which enhances wellbeing. This model was tested in a survey study with 102 older people, whose mean age was 80.3 years and who had migrated to Australia from Asian, European, and Central and South American countries on average 36 years previously. The survey assessed cultural identity, social group memberships acquired post-migration, perceived social support, perceived integration and wellbeing. Results supported the hypothesised model, indicating that joining new heritage culture and wider groups in Australia post-migration provided a platform for social support and integration, which enhanced life satisfaction and reduced loneliness. The implications of these findings for theory and adapting successfully to both migration and ageing are discussed.