Background: Direct Support Professionals (DSP) work closely with individuals with intellectual and developmental disabilities (I/DD) and can play an important role in helping these individuals get treatment when they are also experiencing mental health concerns (MHC). Methods: We employed a systematic review search techniques to identify 15 empirical articles that assessed the outcomes of training programs for DSP that addressed aspects of mental health among individuals with I/DD. Results: There was a wide diversity in the trainings, including both staff and individuals with I/DD focused trainings, workshop formats and intervention formats, and trainings varying in length. Each article found benefits of the training improved knowledge and confidence for the DSP and/or decreased mental health issue symptoms or behaviors for individuals with I/DD. Conclusion: The research reviewed contained various strengths in methodology including mixed methods designs and long follow-up periods; however, there were also pervasive limitations that reflect a need for the field as a whole to devote a more concentrated and collaborative effort to providing high-quality training on the mental health aspects of individuals with I/DD for DSP.