Background: Preterm neonates who are admitted to the neonatal intensive care unit (NICU) undergo several unpleasant treatments as part of their routine care throughout their hospital stay. Nesting positions are supporting techniques that help preterm neonates in the NICU to correct their posture, which may have an impact on their general health. Aim of the study: The current study aimed to determine the effectiveness of nesting positioning on physiological parameters and behavioral state, among preterm neonates in neonatal intensive care unit. Research design: A cross-over experimental research design was used in this study. Setting: The study was carried out in the neonatal intensive care unit at Kafr Eldwar General Hospital, located in El Beheira Governorate, Egypt. Subjects: A convenience sample of 65 preterm neonates was selected for the current study. Tools: Two tools were used for data collection, Tool I: Characteristics and physiological parameters of preterm neonates' assessment tool. Tool II: Assessment of Preterm Neonate's Behavior Assessment Scale. Results: it was obvious that the highest percentages (56.9 % & 78.5 % respectively) of preterm neonates demonstrated normal behavioral response in both supine and prone positions respectively compared to only 9.2% of them in pre-nesting positions. In addition, the preterm Neonatal Behavioral Assessment Scale (NBAS) in the post-prone position positively correlates with physiological parameters observed in premature neonates' post-supine and post-prone assessments. The results indicate statistical significance, with p-values of less than 0.039, 0.018, and 0.033, respectively.  Conclusion: The study concluded that neonatal nesting in prone and supine positions is a simple, noninvasive, and free-of-charge method. It led to improved physiological parameters and neonatal behavioral state. Recommendations: Nesting should be integrated into the routine nursing care of preterm neonates as it is a safe, simple, and noninvasive technique that can enhance their physiological stability and behavioral state. Neonatal intensive care unit nurses should engage in training sessions that emphasize the importance and benefits of using nesting for preterm infants.