Poor adherence of children and adolescents to evidence-based psychosocial interventions remains a fundamental impediment to treatment effectiveness. To maintain client adherence, researchers and clinicians have employed a number of adherence-promoting strategies, from telephone calls and letters to providing transportation costs and child care to motivational enhancement therapies. However, the influence of adherence promoters on intervention outcomes has not been reported. This study examined the moderating effect of adherence-promoting strategies in a survey and meta-analysis of randomized clinical trials of cognitive behavioral treatments, interpersonal therapy, and psycho-education for children and adolescents with mental health problems (k = 33). Results indicated the type and intensity of adherence promoters’ moderated study effect sizes according to client characteristics (age, gender, diagnosis). Preliminary findings suggest that males had higher effect sizes when more intensive adherence-promoting efforts were employed. Adherence-promoting efforts were associated with lower effect sizes for youths who were diagnosed with externalizing disorders. Results of this study suggest directions for future research to clarify clinical guidelines to maximize retention in evidence-based psychotherapy.