Background:Adverse birth outcomes- such as birth defect, prematurity, low birth weight and still birth are closely associated with increased fetal and neonatal mortality, morbidity, and impaired growth and cognitive developmentin both developing and developed countries. Though, there is insufficient information to conclusively assess the magnitude of adverse birth outcome and its associated factors among anemic and non-anemic mothers. Objective: To assessthe magnitude of adverse birth outcome and its associated factors among anemic and non-anemicmothers delivered in Marie stopes International Ethiopia. Methods: Facility-based comparative cross-sectional study was employed by reviewing electronic health record data of 1320 mothers that delivered at Marie stopes International Ethiopia MCHcenters from November 2016 to December 2017. Data was collected from randomly selected 440 lab confirmed anemic and 880 non-anemic mothers from April 25 -May 5, 2018.Descriptive statistics like frequency, percentage, mean and standard deviation was calculated.Logistic regression analysis was employed to identify factors associated with adverse birth outcomes. Those factors that had P-value <0.2 in bivariable analysis were entered into multivariable logistic regression analysis and investigate independent predictors by controlling for possible confounders; significance of statistical association was tested using 95% CI. Findings: In this study, 440anemic and 880non-anemic delivered mothers were involved. The magnitude of adverse birth outcome among anemic mothers was higher than the non-anemic mothers (20.9%, 13.6%) respectively.Motherswho hadlabor duration>24 hours were 2.405 times more likely to have adverse birth outcome than those which had labor duration <=24 hours(AOR 2.405, 95% CI: 1.389, 4.163) and multi- parous mothers were 1.608 times more likely to have adverse birth outcome as compared with primi-parous mothers. (AOR 1.608,95% CI:1.168, 2.213). Conclusions: The magnitude of adverse birth outcome among anemic mothers was higher than the non-anemic mothers 20.9% [95CI17-25] and 13.6% [95CI11.4-15.9] respectively which shows that the magnitude is high. Hemoglobin level <11 g/dl, multi-Parity and labor duration greater than 24 hours were significantly associated with adverse birth outcome. Therefore, early detection and treatment of anemia, to strengthen health education on family planning to prevent repeated pregnancy and to manage long duration of labor is vital.