Nearly half of children meeting criteria for a mental health disorder in the United States (U.S.) do not receive the treatment they need. Unfortunately, lack of access to and engagement in mental health services can be seen at even higher rates for historically marginalized groups, including low-income, racial, and ethnic minority youth. Lay Health Workers (LHWs) represent a valuable workforce that has been identified as a promising solution to address mental health disparities. LHWs are individuals without formal mental health training who oftentimes share lived experiences with the communities that they serve. A growing body of research has supported the mobilization of LHWs to address service disparities around the globe; however, challenges persist in how to scale-up and sustain LHW models of care, with specific barriers in the U.S. In this paper, we describe LHWs' different roles and involvement in the mental health field as well as the current state of the literature around LHW implementation. We integrate the RE-AIM Framework with a conceptual model of how LHWs address disparities to outline future directions in research and practice to enhance equity in the reach, effectiveness, adoption, implementation, and maintenance of LHW models of care and evidence-based practices for historically marginalized communities within the U.S.