Gratitude is a human strength that is beneficial for psychosocial adjustment and academic adjustment. This study aimed to examine the (a) heterogeneity and gender differences in the developmental trajectories of gratitude to obtain a more nuanced understanding of the development of gratitude in children, and (b) relations between these trajectories and psychosocial adjustment, as well as academic adjustment outcomes among Chinese elementary schoolchildren to elucidate the specific benefits of gratitude for children. A sample of 715 children (45.6% girls; M[subscript age] = 8.96 years, SD = 0.76 at Time 1) from 2 Chinese elementary schools completed a packet of measures on 6 occasions across 3 years, using 6-month intervals. Latent Class Growth Modeling revealed 4 heterogeneous developmental trajectory classes of gratitude: High-Increasing, Moderate High-Decreasing, Moderate Low-Increasing, and Low-Stable. Girls were less likely than boys to fall into the Moderate Low-Increasing class or Low-Stable class in reference to the High-Increasing class. Children in the High-Increasing class and Low-Stable class showed the best and the worst psychosocial adjustment and academic adjustment, respectively. The results suggested that gratitude interventions may require adaptations for specific groups, with the Low-Stable class and Moderate High-Decreasing class needing particular attention. Meanwhile, educators aiming to increase elementary schoolchildren's psychosocial adjustment and academic adjustment should consider implementing assessment and intervention programs to promote gratitude early in the school years as well as throughout the elementary school years to prevent trajectories of negative developmental patterns.