Objective: Aplastic anemia is a rare disease but its presence could lead to patient's death and high expenses for hospitals and families. The purpose of this study was to model the economic and health consequences of cyclophosphamide + equine ATG vs. cyclophosphamide for the management of patients with aplastic anemia after bone marrow transplantation at the Social Security Mexican Institute (IMSS). Methods: A cost-effectiveness analysis was developed based on a Bayesian decision tree model from the health care payer's perspective. Effectiveness measures were the rate of avoided acute rejected cases without complications during one-year period and total survival rate on a five-year period. Effectiveness data and transition probabilities were taken from international published literature. Comparators were cyclophosphamide (50mg/kg) + equine-ATG (30mg/kg) and cyclophosphamide (50mg/kg). Resource use was obtained from a local expert panel at IMSS and direct costs were taken from official institutional databases. The model was validated and calibrated according to international pharmacoeconomics guidelines. One-way and probabilistic sensitivity analyses were performed using Monte Carlo Simulation second-order approach. Results: Patients treated with cyclophosphamide + equine ATG experienced the highest clinical success rate with 17.37% while patients with monotherapy experienced 2.63% (p<0.01). Regarding the 5-year survival rate, the combined therapy obtained 80.50% vs. cylophosphamide alone 63.40% (p<0.01). Expected mean cost per patient with cyclophosphamide + equine ATG was US$104,773 and US$102,045 for cyclophosphamide. ICER estimated using the clinical success rate as effectiveness measure was US$185 and using 5-year survival rate was US$159. Within probabilistic sensitivity analyses, components analysis and acceptability curves showed that combined therapy was the most cost-effective therapy when WTP>US$10,000 (p<0.05). Conclusion: In Mexico, the combined therapy is cost-effective for the treatment of aplastic anemia. These results should be taken into account by Mexican decision makers in the management of patients with aplastic anemia after bone marrow transplantation.