Background: Birth weight and duration of gestation are important indicators to predict the future health and survival of newborns. Inappropriate birth weight-for-gestational age can be small-for-gestational-age or large-for-gestational-age. Eventhough inappropriate birth weight for gestational-age is the major cause of neonatal mortality and morbidity little is known about the risk factors. In previous studies, a large birth weight for gestational age was analyzed as normal weight, and this could have resulted in biased estimates. Objective: To assess birth weight for gestational age and associated factors in neonates born at Public Health Facilities in Bahir Dar City, Northwest Ethiopia, 2020. Methods: Institution based cross-sectional study was conducted among 731 neonates from November 28, 2020 to January 1, 2021. Participants were selected using systematic randome sampling technique. A pre-tested interviewer administrative questionnaire was used. Data were entered into Epi data version 3.1 and exported to SPSS version 23 for further analyses. A multinomial logistic regression model was fitted to identify the associated factors. Variables with P-value <0.05 in multivariable analysis was used to declare as statistically significant. The odds ratio (OR) with at 95% confidence interval (CI) was used to measure the strength of association. Results: Over all, inappropriate birth weight for gestational age was 36.9% (95% CI: 33.4%-40.4%). Small for gestational age and large for gestational age was 23.8 %( 95%CI: 20.7%-26.9%) and 13.1 % (95% CI: 10.5%-15.5%) respectively. Neonates whose mothers’rural resident (AOR= 2.21, 95% CI: 1.37-3.58), being female (AOR=1.46, 95% CI: 0.99-2.05), and whose mothers had took additional food during index pregnancy (AOR=0.63, 95% CI:0.44-0.91) were more likely to be small for gestational age, neonates whose mothers had medical illness during index pregnancy(AOR =2.32, 95% CI: 1.13-4.77), were more likely to be large for gestational age. Conclusion: The proportions of small-for-gestational-age and large-for-gestational-age were high. Rural resident, being female and took additional food during the index pregnancy were associates of small for gestational age and medical illness during the index pregnancy were assocaites of large birth weight. Health Care Professionals should give nutritional advice for rural residence women during antenatal care Keywords: -Small, large, gestational age, birth weight, Bahir Dar city