Nursing homes in USA serve patients with serious mental illness (SMI), such as schizophrenia and bipolar disorder, but poor quality is common in nursing homes where patients with SMI are treated. The objective of this national study is to support equitable quality in USA nursing homes by providing information that can help target government and industry initiatives aiming to improve quality in nursing homes that serve individuals with SMI. The specific aims of this study are to identify nursing home characteristics, care processes, and quality outcomes that differ across nursing homes with higher versus lower proportions of patients with SMI. National 2010 nursing home data from several government sources and compiled in a single analytic file are examined. Nursing homes are compared by proportion of patients with SMI. Findings show nursing homes with higher versus lower proportions of patients with SMI differ in many ways, such as having a greater likelihood of being for-profit, lower registered nursing hours per patient day, a greater proportion of residents restrained, younger patient populations, fewer female and more black patients, more patients on Medicaid, fewer admissions from acute care hospitals, and higher percentages of long-stay patients reporting daily pain. Findings provide a national view of nursing homes with higher versus lower proportions of patients with SMI. This study can help steer policymakers to focus on key types of nursing homes, and providers to focus on key care processes and outcomes, when aiming to improve the quality of nursing homes that serve individuals with SMI.