This study draws upon organisational psychology and platform labour research to investigate how socio-psychological factors affect the mental well-being of platform workers and help them cope with the challenges of work. Based on a survey study of 500 food-delivery workers (“riders”) in China, we provide quantitative evidence of workers’ ambivalent subjective experience that complements the predominantly qualitative account in the extant literature. In particular, we assess the complex relationships between meaningfulness of work, autonomy at work, self-perceived competence, and workers’ subjective well-being. Our data also show that the stress-buffering effect of social support mainly comes from the riders’ familial contact and their online group chat with other workers. Overall, despite the well-documented precarity and stress in platform work, the riders in our sample appear to be able to mobilise inner and relational resources to achieve a relatively high-level mental well-being.