In China, older migrant workers represent an especially vulnerable group, facing challenges to their quality of life as they grow older and move away from their hometowns. This study aimed to investigate the relationship between social integration, subjective well-being, and subjective fairness over a four-year period in a cohort of 1,394 older Chinese migrant workers aged 50 and older. Latent growth modeling showed a significant positive change over time in all three psychosocial constructs. Additionally, the parallel process latent growth modeling revealed that social integration had an indirect effect on subjective fairness by positively affecting subjective well-being, both at baseline and longitudinally. These findings highlight the crucial roles of social integration and subjective well-being in shaping subjective fairness over time in this marginalized population. Fostering social inclusion and emotional health of older migrants may have cascading benefits for social fairness. The complete longitudinal mediation suggests that improved subjective well-being serves as a mechanism translating increasing social integration into enhanced subjective fairness across the later stages of life. This study adds to our understanding of the psychological factors that can be modified to promote subjective fairness and perceived equality in migrant worker populations.