Background & Objective: Considerable support exists for higher-order dimensional conceptualizations of psychopathology in adults. A growing body of work has focused on understanding the structure of general and specific psychopathology in children and adolescents. No prior meta-analysis has examined whether the strength of the general psychopathology factor (p factor)—measured by explained common variance (ECV)—changes from childhood to adolescence. The primary objective of this multilevel meta-analysis was to determine whether general psychopathology strength changes across development (i.e., across ages). We hypothesized a decrease in general psychopathology strength across development, reflecting developmental differentiation with age.Methods: Several databases were searched in November 2021; 65 studies including 110 effect sizes (ECV), nested within shared data sources, were identified. Included empirical studies used a factor analytic modeling approach that estimated latent factors for child/adolescent internalizing, externalizing, and optionally thought-disordered psychopathology, along with a general factor.Results: Age-moderation analyses revealed that general factor strength remains stable across ages, and that general psychopathology explains about 56% of the reliable variance across ages.Conclusions: Contributions of general psychopathology do not significantly change from ages 2–17. Even if the structure of psychopathology changes with development, the prominence of general psychopathology across development has important implications for future research and intervention.