Introduction: Adverse childhood experiences (ACEs) are prevalent and have been linked to problematic social media use (PSMU) in adolescents. However, few prior studies focused on the longitudinal association and the functional nature between ACEs and PSMU. Drawing on the Compensatory Internet Use Theory and the Cumulative Risk Hypothesis, this study aimed to examine the relation between ACEs and PSMU as well as the cumulative effects of ACEs on PSMU using a three-wave longitudinal design with multiple informant assessments of adolescent PSMU. Methods: A total of 264 Chinese adolescents (50.0% female; M[subscript age] = 13.91 years, SD = 0.76) and 234 parents (75.0% female; M[subscript age](206) = 41.00 years, SD = 3.65) participated in the baseline measurement. Two separate sets of generalized linear mixed models (GLMMs) were performed to test the effects of ACEs on adolescent-reported and parent-reported PSMU. Results: Results from the GLMM analyses revealed that (1) exposure to ACEs significantly predicted adolescent-reported PSMU (b = 0.17, p < 0.01), but not parent-reported PSMU (b = 0.03, p = 0.65), and (2) the functional relation between cumulative ACEs and PSMU followed a linear pattern, irrespective of whether PSMU was reported by adolescents or parents. These findings provided empirical support for the Cumulative Risk Hypothesis, specifically aligning with the additive (linear) model. Conclusions: Earlier ACE exposure predicts subsequent adolescent PSMU; the functional relation between cumulative ACEs and PSMU is linear. This underscores the importance of addressing each ACE in prevention and intervention efforts aimed at mitigating adolescent PSMU.