The 2019 National Survey on Drug Use and Health reports that 9.5 million Americans aged 18 and older have been diagnosed with more than one mental disorder. Music therapists working in mental health treatment settings are likely to work with individuals who have a complex diagnosis defined here as 2 or more of the following: depression, eating disorder, generalized anxiety disorder, substance use disorder, and severe mental illness. Additionally, adverse childhood events or posttraumatic stress disorder often complicate the clinical profile. Given this, a trauma-informed approach to music therapy treatment is necessary to improve outcomes and minimize harm. The risks, contraindications, and ethical considerations necessary to effectively treat and care for these clients in music therapy will be reviewed. Methods of identifying, assessing, and treating these complex clinical issues in music therapy are discussed with the goal of helping clinicians understand: (1) where treatment needs to begin to ensure therapeutic goals addressing primary issues prior to addressing secondary issues and (2) the appropriate use of music therapy methods. The necessity for music therapists to understand the power of the music in the music therapy process is explored, to ensure that clinicians are meeting client needs, not triggering symptomatology, traumatic memories, or experiences. The importance of a clinician knowing their scope of practice, when they are adequately trained and prepared to work with clients with complex disorders, and how to utilize support such as consultation and supervision to support their effective treatment with client(s) is presented.