OBJECTIVES: A previous study indicated that increasing nurse staffing levels in Belgian general cardiac postoperative nursing units was associated with lower mortality rates. The aim of this study is to conduct a cost-effectiveness analysis of increasing nurse staffing levels to the level of the 75th percentile in Belgian general cardiac postoperative nursing units from a hospital perspective.  METHODS: The intervention was an increase in the number of nursing hours per patient day to the 75th percentile for nursing units staffed below that level. The comparator was a ‘do nothing’ alternative. Data on nurse staffing levels were extracted from the Belgian Nursing Minimum Dataset and data on in-hospital mortality from the Belgian Hospital Discharge Database. The number of life-years gained was calculated by multiplying the number of avoided deaths by the life expectancy of patients having a coronary artery bypass graft and patients having heart valve procedures. To this effect, survival rates were derived from the literature. National cost estimates for the year 2007 were used. Results were expressed in the form of the additional costs per avoided death and the additional costs per life-year gained. RESULTS: The costs of increasing nurse staffing levels to the 75th percentile in Belgian general cardiac postoperative nursing units amounted to €1,211,022. Such nurse staffing levels would avoid an estimated number of 45.9 (95% CI: 22.0 – 69.4) patient deaths per year and generate 458.86 (95% CI: 219.93 – 693.79) life-years gained annually. This corresponds with incremental cost-effectiveness ratios of €26,372 per avoided death and €2,639 per life-year gained. Sensitivity analyses indicated that the incremental cost-effectiveness ratio was robust to changes in input parameters. CONCLUSIONS: Increasing nurse staffing levels appears to be a cost-effective intervention as compared to other cardiovascular interventions.