Research Findings: One strategy to support early childhood providers' work with children exhibiting challenging behavior is offering mental health consultation services in order to build staff skills and confidence and reduce staff stress and turnover. Through systematic search procedures, 26 recent studies were identified that addressed the effectiveness of early childhood mental health consultation with respect to staff- and program-level outcomes. Across the reviewed studies, there is some evidence that early childhood mental health consultation helped increase staff self-efficacy/confidence and competence in dealing with troubling or difficult behaviors of young children in their care. In several studies, staff receiving consultation had improved sensitivity and lower job-related stress. In addition, consultation generally helped improve overall quality of early care and education settings and was linked to reduced staff turnover. Practice or Policy: Because the majority of the studies were not in peer-reviewed publications, this research synthesis underscores the importance of increasing the rigor of future studies to provide policymakers and practitioners with better evidence on consultation effectiveness. Priorities for future research include articulating the theory of change underlying consultation activities; developing additional measurement instruments to explore key components of mental health consultation; and examining the effects of consultant qualifications, consultation intensity, and specific activities on outcomes. (Contains 2 tables.)