Children in foster care suffer from an extremely high prevalence of mental health problems, yet, it remains unclear if they consistently use mental health treatments, such as therapy. To determine whether these children receive treatment more often when they have specific types of mental health problems, we examined the prevalence and associations between mental health problems, as identified by standardized screening, and mental health treatment utilization. Using descriptive statistics, multivariate models, and moderation and exploratory mediation analysis, we analyzed data for 237 children in foster care, aged 5–17 years. We found 71 % were identified with a mental health problem in at least one of the sub-domains examined (emotional, conduct, inattention/hyperactivity, peer, and prosocial), and 61 % of children received mental health treatment (p = .001). Yet, the only sub-domains predictive of treatment utilization were peer problems (p = .004) and low prosocial behaviors (p = .030). Moderation analysis revealed that the relation between peer problems and treatment utilization was strongest among white children (p = .012). Exploratory mediation analysis suggested that peer problems may increase the likelihood of treatment for children with emotional (95 % CI 0.05, 0.53) and conduct problems (95 % CI 0.05, 0.58). It remains unknown whether this occurs because peer problems are associated with overt symptoms, or because peers problems can exacerbate existing social–emotional problems. Routine screening for mental health problems among children in foster care can facilitate timely treatment, and potentially improve the present and future quality of life for this high risk population.