Background: Severe acute malnutrition is one of the major public health problems in developing countries having a devastating effect on the lives of many children under 5 years of age. In Ethiopia, there has been isolated studies conducted on malnutrition with no study attempting to identify the determinants of severe acute malnutrition in the rural district of Enebsie Sarmidr.This study intends to identify the determinants of severe acute malnutrition in rural district located in North West Ethiopia. Methods: A Community based un matched case -control study was carried on 311 (64 cases and 247 controls) children aged between birth-59 months with their respective mothers or care takers from March 1-30/ 2016. Odds Ratio along with 95% confidence interval was estimated to identify determinants of severe acute malnutrition using the multivariable logistic regression. Results: The response rate was 97.8%. Severe acute malnutrition was significantly associated with age groups birth-24 months (AOR = 2.64, 95% CI 1.17-5.95), late initiation of breast feeding greater than an hour after birth (AOR = 4.26, 95% CI 1.74-10.42), nonexclusive breast feeding (AOR =5.81, 95% CI 1.80-18.79), diarrheal disease in the preceding 2 weeks before SAM (AOR = 7.98, 95% CI 2.57-24.74), febrile illnesses preceding 2 weeks before SAM (AOR = 2.87 95% CI 1.13-7.63), decreased or maintained mealing of the mother compared to the regular during pregnancy or lactation (AOR = 8.15, 95% CI 3.70-17.98) and birth interval less than 2 years (AOR = 3.34, 95% CI 1.55-7.20) after controlling other variables effect. Conclusion: A child's age, late initiation of breast feeding, nonexclusive breast feeding, diarrheal diseases and febrile illnesses preceding 2 weeks before SAM, decreased or maintained mealing compared to the regular during pregnancy and lactating of the mother and narrow birth interval were identified as determinants of SAM. Therefore, collaborative efforts are needed to improve promotion of better child caring practices specifically, child and maternal feeding practices and prevention and treatment of acute illnesses.