<p>While the adverse effects of economic inequality on prosocial behavior have been well-documented, the dynamic processes and underlying mechanisms during emerging adulthood remain equivocal. Whether this relation is consistent across different socioeconomic status groups also awaits to be unveiled. To address these gaps, this three-year longitudinal study shed light on the developmental nature of subjective economic inequality, trust, as well as prosocial behavior, and the nuance within such associations across low- and high-socioeconomic status groups. This study collected data from 1065 Chinese emerging adults (649 females; <i>M</i>_age = 18.34 years, <i>SD</i> = 0.77) at Time 1, with 981 (attrition rate = 7.88%), 874 (attrition rate = 10.91%), and 830 (attrition rate = 5.03%) participating in Time 2, Time 3, and Time 4, respectively. Results of latent growth modeling found that subjective economic inequality increased, whereas trust and prosocial behavior declined over time. Initial levels of subjective economic inequality were indirectly through initial trust linked to the initial levels of and changes in prosocial behavior. Multi-group results revealed that in the high-socioeconomic status group, initial subjective economic inequality affected subsequent growth in prosocial behavior via changes in trust, whereas in the low-socioeconomic status group, the effect occurred through initial trust. These findings highlight that declining trust is the central mechanism by which subjective economic inequality reduces prosocial behavior, with different influencing pathways across socioeconomic status groups in the Chinese cultural context.</p>