Traditional reviews and previous meta-analyses of self-concept interventions have underestimated effect sizes by using an implicitly unidimensional perspective that emphasizes global self-concept. In contrast, this research employed a synergistic blend of meta-analysis and multidimensional construct validation to evaluate the impact of self-concept interventions for children in 145 primary studies (200 interventions). Overall, interventions were significantly effective (d = 0.51, 460 effect sizes). However, in support of the multidimensional perspective, interventions targeting a specific self-concept domain and subsequently measuring that domain were much more effective (d = 1.16), suggesting sole reliance on global self-concept is inappropriate for evaluating interventions designed to enhance a specific component of self-concept. Other moderators (e.g., feedback, experimental design, target population groups) also influenced effect sizes in ways useful to the design of new interventions. Methodologically, this research also demonstrates the use of both fixed and random effects models and incorporation of multiple outcomes from the same study.