Individuals with severe mental illness (SMI) including schizophrenia and bipolar disorder are dying younger than the general population; cancer is a leading cause of death in this population. People with SMI have higher rates of dying from breast, lung, and colon cancer, and disparities in treatment appear to be one contributing factor. Individuals with SMI may be diagnosed with more advanced stage cancer and less likely to receive stage-appropriate cancer treatment. Although collaborative care models integrating medical and psychiatric care have shown promise in other populations, the challenge of treating SMI and cancer is distinct and relatively understudied. Patients may have uncontrolled psychiatric symptoms that can impact their understanding of their diagnosis and treatment decisions. Oncologists have less training and inadequate time to address multiple unmet needs. Mental health care is frequently fragmented from cancer care.