There is a significant challenge in predicting the duration of the neonatal hospital length of stay (LOS) due to the complicated factors that affect newborns. Most studies are conducted among pre-term neonates, in which the gestational age is lower than 37 weeks and the birth weight of patients is considered a major risk factor for a prolonged LOS. No previous systematic review of the literature was conducted among the full-term population. This review aims to determine the risk factors for neonatal intensive care unit (NICU) LOS from multiple studies affecting full-term patients. The included studies focused on assessing reasons and factors affecting the NICU LOS of newborns, including "full-term newborns." We included studies that considered the NICU LOS as the primary outcome. Both retrospective and prospective studies were eligible for inclusion. The risk of bias for the included studies was evaluated using the Quality in Prognosis Studies (QUIPS) tool suggested by the Cochrane Prognosis Methods Group. The literature search of the databases identified 637 potentially relevant articles, among which 10 met the inclusion criteria and were selected for this review. Among the 10 studies, three risk factors were identified: disease-related, parent-related, and inherent factors. These factors constitute a critical risk factor most widely studied and consistently associated with LOS for the full-term population. Our findings offer an updated extensive summary of this aspect that has not been considered in detail in the literature. In conclusion, several critical risk factors affecting neonatal LOS were discovered in the published studies in this systematic review. However, there is a need for more prospective studies with standardized approaches that are crucial to confirm these findings and help develop effective interventions.