Background Nutritional care during the neonatal period is a cornerstone towards achieving optimal care. However, very limited data is available on optimizing parenteral and enteral nutrition that directly affects infant survival among Ethiopian neonates. Therefore, the objective of this study is to identify determinants of time to full enteral feeding achievement among low-birth-weight neonates admitted to neonatal intensive care units of public hospitals in Hawassa city. Methods A facility-based retrospective cohort study was conducted in Adare general hospital and Hawassa University’s comprehensive specialized hospital from August 2018 to 2019. Charts of infants with a birth weight of 1000-2000g (n = 273) neonates who were admitted to the neonatal intensive care unit (ICU) were reviewed. The sample size for each hospital was allocated proportionally and subjects were selected by using a simple random sampling technique. Data were entered using Epi. data version 3.1, and analysis was performed using SPSS version 20. Kaplan-Meier estimator and a Cox proportional hazard model were used. Result The mean (SD) age when an enteral feed (trophic feeding) was first commenced was 2.13(1.373) days. The median time to achieve full enteral feeding was 8 days with IQR (7–10 days). Gestational age reduces the time to full enteral feeding by 18.8% for each additional week of gestation (AHR = 0.812, p-value = 0.003). The time to achieve full enteral feeding was shorter by 70.4% among neonates who were small for gestational age, as compared with that appropriate for gestational age (AHR = 0.296, p-value<0.001). Conclusion According to this study, the time that the neonate takes to achieve full enteral feeding was relatively short. Gestational age and weight for gestational were the determinants for time to full enteral feeding achievement. Further research needs to be conducted to explore further, in addition to current findings.