Background: Low birth weight (LBW), according to WHO, defined as an infant weighing less than 2500g at birth, poses significant global health concerns. It contributes to increased morbidity and mortality rates in newborns, with long-term implications for health and development. Objective: To determine factors associated with low birth weight among mothers who gave birth in public hospital, in Addis Ababa, Ethiopia. Methods: facility based Un-matched case-control study design was conducted among women who delivered in public hospitals of Addis Ababa city. Data was collected using a structured questionnaire through interview and medical record review of mothers. Sample size was calculated by Epi-info version 7.0 to get a final sample size of 275(cases=85 and controls=190). SPSS version 20 was used for analysis. Bivariate and multivariate logistic regression analysis was used to determine the effect of the independent variables on birth weight. Presence of significant association was determined using OR with its 95%CI. A P value of less than 0.05 was considered to declare statistical significance. Table, graphs and texts were used to present the data. Results: Multivariable binary logistic Regression analysis was computed to identify the association between potential factors with new born birth weight. In the multivariable logistic regression, newborn babies with gestational age of below 36 were strongly linked to low birth wight (AOR=28, 95% CI: 10.74, 75.5). Conversely, mothers who avoid heavy work load (AOR= 3.8, 95%CI (3.8 (1.2, 12.4)) notably, the risk of low birth weight was significantly higher for mothers with shorter gestation and high workload during the pregnancy period. Conclusion : The study confirmed that Gestational age, Intended (planned) Pregnancy, Taking Iron/folate, Taking coffee, Taking additional food, Workload during pregnancy, Illness during pregnancy, and Getting professional Advice during the pregnancy were found to be significantly associated with low birth weight. Key words: dietary diversity, low birth weight