Background: Female genital mutilation involves the partial or total removal of external female genitalia or other injuries to the female genital organs for non-medical reasons. Studies conducted in developed countries have shown that deinfibulation is associated with positive obstetric outcomes. However, no research has been done to examine the effects of deinfibulation compared to type I FGM on obstetric and neonatal outcomes in Ethiopia. Objectives: The study aim was to examine if there were significant differences between de- infibulated and type I FGM women in the risks of developing adverse birth outcomes in the Afar region, Northeast Ethiopia Methods: An institution-based comparative cross-sectional study supplemented by a qualitative study was conducted among 215 deinfibulated and 215 type I FGM women coming for delivery service at public hospitals in Afar region. The participants in the study were chosen by systematic random sampling. A semi-structured interviewer-administered questionnaire was used for data collection. Data entry and analysis was done by Epidata 3.1 and SPSS 20, respectively. Tables and frequencies were used to present the descriptive data. Binary logistic regression model with bi-variate and multivariable analysis was used to identify factors. Statistical association was determined by using odds ratio at 95% CI and P-value <0.05 was cut-off point for significant association. The qualitative data was coded in themes and analyzed thematically. Result: The proportion of adverse birth outcome among deinfibulated women were 43.26% (95% CI; 36.58–49.93), while among type I FGM women were 22.33% (95% CI;16.71– 27.94). Not receiving ANC (AOR = 3.24, 95% CI: 2.61–5.89], Type III FGM(deinfibulated) (AOR=3.77, 95%CI, 2.29-6.21), Being primigravida (AOR=2.01, 95%CI, 1.22-3.59) were significant predictor of adverse birth outcome. Lack of counseling, work overload, and lack of husband support were identifed themes as hindrance of deinfibulation service utilization. Conclusion and recommendation: Despite deinfibulation use, infibulated women's risk of adverse outcomes remains high. ANC, gravidity, and type of birth attendant were mainly associated with adverse birth outcomes. Quality obstetric follow-up with specialized care for infibulated women, such as deinfibulation, may help reduce obstetric complications. Key Words: Female genital mutilation; Deinfibulation; Childbirth, Adverse birth outcome