["Population, Space and Place, Volume 32, Issue 3, April 2026. ", "\nABSTRACT\nIn addition to developed nations, the challenges of population ageing and declining fertility have also intensified in populous East Asian regions, prominently represented by China. Migrants serve as a critical urban labour resource in these countries and territories, and their fertility intentions directly affect long‐term population equilibrium and regional sustainability in destination areas. Drawing on two waves of the China General Social Survey (CGSS), this study investigates the mechanisms through which social integration shapes migrants' fertility intentions. A particular focus is placed on the mediating role of perceived fairness. Using a long‐difference model supplemented by heterogeneity analyses and mechanism tests, multiple pathways are identified that link social integration to migrants' fertility intentions. The findings reveal that: (1) Social integration tends to suppress migrants' fertility intentions, but perceived fairness partially buffers this effect and reshapes the decision logic. (2) Heterogeneity analyses show that new‐generation migrant workers exhibit higher fertility intention as social integration rises, a finding consistent with a strategic pursuit of urban identity via childbearing. Meanwhile, social integration has a homogeneously suppressive effect among migrants across educational groups and among those with rural Hukou. (3) During periods of fertility‐policy relaxation, lagging support services failed to translate into institutional trust, which in turn weakened policy effectiveness. Based on these distinct pathways, this study proposes multi‐level policy recommendations, offering insights and suggestions for migrant‐dense, ageing‐before‐affluent developing countries.\n"]