Abstract Objectives This study aimed to examine the mediating effect of perceived social support in the relationship between loneliness and social isolation among Chinese older adults relocated for poverty relief. Methods We surveyed 128 older migrants from four resettlement areas in Guizhou Province, southwest China. A general information questionnaire, the Lubben Social Network Scale‐6, the Perceived Social Support Rating Scale, and the Single Item Loneliness Scale were used in our study. We also used the SPSS macro PROCESS to test a mediation model and the Bootstrap method to assess its significance. Results The prevalence of social isolation among older relocators was 85.9%; the mediation model showed that loneliness had a direct negative effect on social isolation ( B = −1.25, p < 0.01), and that perceived social support fully mediated this effect (−1.18), with a total effect of −1.25 ( p < 0.01) and a mediating proportion of 94.4%. Conclusions Older relocators in poverty alleviation areas experienced high levels of social isolation. Perceived social support might buffer the negative impact of loneliness on social isolation. We suggest that interventions should be designed to enhance perceived social support and reduce social isolation among this vulnerable population.