Severe and persistent mental illness with psychotic features as a comorbidity to a cancer diagnosis presents unique challenges to delivery of cancer care. Current literature suggests that there are poorer outcomes and higher mortality in patients with severe mental illness, partly explained by barriers to access of screening services and social vulnerability factors. However, cancer care is also delivered differently in patients with SMI, and often less aggressive care is offered. These healthcare disparities could be addressed in part by preparing for the ethical issues that can arise during the course of care. Cancer care staff may have limited experience and knowledge about treatment of psychiatric symptoms and may feel troubled in scenarios when patients lack capacity and become unwilling to participate in their care. Conversely, patients may benefit from early involvement of their mental health team for psychiatric optimization and contingency preparation. Specifically, preemptive planning between the cancer care team and the mental healthcare team can alleviate distress for the patient and healthcare teams alike. This is especially important when medical decision-making capacity can fluctuate during treatment. A person-centered, team-based approach to care delivery provides bidirectional empowerment. A process is proposed to enhance medical decision-making in patients with severe mental illness and cancer. It is imperative to acknowledge the disparities that exist in this patient population and create a process that will improve care and alleviate distress for the patient and the cancer care team.