Parents may develop burnout when they chronically lack the resources to handle parenting stressors. Although the relationship between parental burnout and child-related variables has been explored, its impact on adolescents’ development remains unknown. This study investigates the effect of mothers’ parental burnout on social adaptation and security in adolescents, and the mediating roles of mothers’ parenting styles. Questionnaires were distributed to adolescents and their mothers at three time points with an interval of six weeks. In the first survey, 916 mothers completed a parental burnout assessment. In the second, 1054 adolescents completed maternal rejection and maternal autonomy support scales, and a Harsh Parenting assessment. In the third, 1053 adolescents completed Children and Adolescent Social Adaptation and Security Questionnaires. In total, 411 paired data points were matched (mothers’ age: M = 42.1, SD = 4.65; adolescents’ age: M = 13.1, SD = 0.52). The results of bootstrapping indicated the following: (1) Mothers’ parental burnout negatively predicted adolescents’ social adaptation and security. (2) Mothers’ parenting styles of rejection, harsh parenting, and autonomy support mediated the relationship between parental burnout and social adaptation and security. These findings confirmed the importance of mothers’ influence on adolescents’ parenting activities. Therefore, the enrichment of parenting resources and a decrease in the use of negative parenting styles may promote the healthy psychological development of the children of mothers facing parental burnout.