Objective: Open repair (OPEN) and conservative management (CONS) have been the treatments of choice for splenic artery aneurysms (SAAs) for many years. Endovascular repair (EV) has been increasingly used with good short-term results. In this study, we evaluated the cost-effectiveness of OPEN, EV, and CONS for the treatment of SAAs. Methods: A decision analysis model was developed using TreeAge Pro 2013 software (TreeAge Inc, Williamstown, Mass) to evaluate the cost-effectiveness of the different treatments for SAAs. A hypothetical cohort of 10,000 55-year-old female patients with SAAs was assessed in the reference-case analysis. Perioperative mortality, disease-specific mortality rates, complications, rupture risks, and reinterventions were retrieved from a recent and extensive meta-analysis. Costs were analyzed with the 2014 Medicare database. The willingness to pay was set to $60,000/quality-adjusted life years (QALYs). Outcomes evaluated were QALYs, costs from the health care perspective, and the incremental cost-effectiveness ratio (ICER). Extensive sensitivity analyses were performed and different clinical scenarios evaluated. Probabilistic sensitivity analysis was performed to include the uncertainty around the variables. A flowchart for clinical decisionmaking was developed. Results: For a 55-year-old female patient with a SAA, EV has the highest QALYs (11.32; 95% credibility interval [CI], 9.52-13.17), followed by OPEN (10.48; 95% CI, 8.75-12.25) and CONS (10.39; 95% CI, 8.96-11.87). The difference in effect for 55-year-old female patients between EV and OPEN is 0.84 QALY (95% CI, 0.42-1.34), comparable with 10 months in perfect health. EV is more effective and less costly than OPEN and more effective and more expensive compared with CONS, with an ICER of $17,154/QALY. Moreover, OPEN, with an ICER of $223,166/QALY, is not cost-effective compared with CONS. In elderly individuals (age > 78 years), the ICER of EV vs CONS is $60,503/QALY and increases further with age, making EV no longer cost-effective. Very elderly patients (age >93 years) have higher QALYs and lower costs when treated with CONS. The EV group has the highest number of expected reinterventions, followed by CONS and OPEN, and the number of expected reinterventions decreases with age. Conclusions: EV is the most cost-effective treatment for most patient groups with SAAs, independent of the sex and risk profile of the patient. EV is superior to OPEN, being both cost-saving and more effective in all age groups. Elderly patients should be considered for CONS, based on the high costs in relation to the very small gain in health when treated with EV. The very elderly should be treated with CONS.