Emerging evidence suggests that integrated care models are associated with improved mental health care access and outcomes for youths (children ≤12 years and adolescents 12-21 years) served in pediatric primary care settings. However, the key components of these complex models remain unexamined. To identify and describe the key components of effective pediatric integrated mental health care models. The PubMed, Embase, PsycINFO, and Cochrane Controlled Register of Trials electronic databases were searched for relevant peer-reviewed articles published between January 1, 1985, and April 30, 2019. Articles were restricted to those published in the English language. Eligible articles reported original data on youths 17 years or younger, implemented an integrated mental health care model in a pediatric primary care setting, and assessed the model's association with primary outcomes (eg, mental health symptom severity) and secondary outcomes (eg, functional impairment and patient satisfaction). Articles that specified some degree of systematic coordination or collaboration between primary care and mental health professionals were included in the final review. Two independent reviewers extracted data on study design, model type, model components, level of integration, and outcomes. Study quality was assessed using the Jadad scale. Data were analyzed between January 1, 2018, and May 31, 2019. Eleven randomized clinical trials involving 2190 participants were included. Three studies focused on youths with depression, 3 on youths with attention-deficit/hyperactivity disorder, and 5 on youths with behavioral disorders. Most studies (9 of 11) implemented either the collaborative care model (n = 3), a slightly modified version of the collaborative care model (n = 2), or colocated care (n = 4). The most commonly reported components of effective pediatric integrated mental health care models were population-based care, measurement-based care, and delivery of evidence-based mental health services; all 3 components were present in studies reporting clinical improvement of mental health symptoms. Other model components, such as treatment-to-target or team-based care, were common in studies reporting specific outcomes, such as functional impairment. This review is the first to date to systematically search and qualitatively synthesize information on the key components of effective pediatric integrated mental health care models. This knowledge may be especially useful for pediatric primary care administrators in the selection of an integrated care model for their setting.