ABSTRACT   BACKGROUND: Low birth weight and prematurity are associated with increased morbidity, mortality and multiple short and long-term complications, exerting impacts on the individual, the families, the community and the health care system. Fetal, maternal and environmental factors have been associated with low birth weight and prematurity, based primarily on researches from high-income countries. It is unknown whether these risk factors are the same in low and middle income countries. The aims of this study are to determine the prevalence of low birth weight and prematurity and associated factors in Jimma University Specialized Hospital, Ethiopia. METHODS: This observational study was conducted at Jimma University Specialized Hospital, Ethiopia, from December 2014 to September 2016. Multivariable logistic regression was used to determine the associated factors, with results reported as odds ratios (OR) and 95% confidence intervals (CI). RESULTS: The prevalence of low birth weight and prematurity were 14.6% and 10.2%, respectively. The mean birth weight was 2,975g (standard deviation 494). Prematurity (OR 23.54, 95%CI 15.35-36.08, p<0.001) and unmarried marital status (OR 5.73, 95%CI 1.61-20.40, p=0.007) were positively associated with low birth weight. Female sex (OR 1.69, 95%CI 1.18-2.42, p=0.004) and unmarried marital status (OR 4.07, 95%CI 1.17-14.14, p=0.027) were positively associated with prematurity. CONCLUSION: The prevalence of lower birth weight and prematurity in this study is lower than other studies reported from similar facilities. Prematurity and unmarried marital status are associated with LBW whereas female sex and unmarried marital status are associated with prematurity in this population. Key words: prematurity, low birth weight, newborn