Prior research has shown that lower nurse-to-patient ratios are associated with increased patient mortality. This cross-sectional analysis using multiple data sources from four states assessed the relationship between nurse staffing and survival disparities after in-hospital cardiac arrest. Results indicate that disparities in survival between Black and white patients may be linked to medical-surgical nurse staffing levels, and that the benefit of being treated at a hospital with higher staffing ratios may be especially pronounced for Black patients.