Background: - First trimester safe abortion is a process of terminating early pregnancy up to 12 weeks of gestational age by using either of medical or surgical procedures. Despite increasing the access, consumption and popularity these services in Ethiopian health facilities, their economic implications has been poorly understood and the cost effective alternative method hasn’t been identified. Objective: - The aim of this study was to identify the cost-effective first trimester safe abortion service, medical and surgical given to women in Bahir Dar health facilities; 2020 Methods: - Institution based comparative cross sectional cost effectiveness analysis was conducted to identify the cost-effective first trimester safe abortion services, medical and surgical given to women in Bahir Dar health facilities. Two hundred fifty four first trimester pregnant women were selected in both arms using systematic random sampling technique. Pretest was done and training was given. Micro costing and human capita approach were costing methods from provider’s perspective. Decision tree was created by model built excel. Socio-demographic and reproductive related data was summarized using descriptive statistics. The cost effectiveness results were summarized and presented by using average cost-effectiveness ratio and cost-effectiveness scatterplot. One way sensitivity analysis was done. Result: 123 and 122 first trimester pregnant women were included in medication and surgical abortion services respectively. 106 in medication and 103 in surgical abortion were completed abortion. The health facilities incurred a total of US$3,430.66 and US$4,145.83 for medication abortion and surgical abortion respectively. The total cost incurred by health facilities per service were US$27.9 in medication and US$34.87 in surgical. The average cost incurred by health facilities per complete abortion were US$32.4 in medication abortion and US$40.3 in surgical abortion. Conclusion: - The finding of this study demonstrates that medication abortion service was cost effective. The health facilities incurred US$27.9 per service in medication abortion and US$34.87 per service in surgical abortion. The health facilities incurred US$32.4 per complete abortion in medication abortion and US$40.3 per complete abortion in surgical abortion. Key words: - First trimester safe abortion services, cost-effectiveness analysis, average cost effectiveness ratio and one way sensitivity analysis