The aim of this study was to investigate associations between specific mental health problems and pubertal stage in (pre)adolescents participating in the Dutch prospective cohort study TRAILS (first assessment: N = 2230, age 11.09 [plus or minus] 0.56, 50.8% girls; second assessment: N = 2149, age 13.56 [plus or minus] 0.53, 51.0% girls). Mental health was assessed by the Youth Self-Report, pubertal (Tanner) stage by parent-rated drawings of secondary sex characteristics. Overall, higher Tanner stages were related to more reported tiredness, irritability, rule-breaking behaviors, and substance use; and fewer fears and somatic complaints. Girls showed increases in social uncertainty, depressed mood, and worries; boys a decrease in self-criticism. Increasing problems during puberty were mostly related to the process of physical maturation, whereas decreasing problems were rather related to general age-related developments. Pubertal timing was associated with different symptoms than pubertal status or age. Puberty seems to affect girls more negatively than boys. (Contains 3 tables and 1 figure.)