Background: Developmental care consists of modifying the neonatal intensive care unit to reduce stress and improve the optimal mind and behavioral development of the preterm neonate. Aim: Evaluate the effect of preterm neonates' developmental supportive care on behavioral cues of preterm neonates. Research design: A quasi-experimental design was used. Sample: a convenient sample of 50 preterm neonates, in addition and 50 nurses who were responsible for providing care for those preterm neonates. Setting: In the Neonatal Intensive Care Unit (NICU) of Maternity University Hospital at El-Shatby in Alexandria. Method: Preterm neonates' behavioral cues were evaluated before the implementation of developmental care of preterm neonates. Heart rate, respiration, and oxygen saturation were documented immediately before, immediately after, and ten minutes after receiving developmental supportive care by the nurses. Tools: three tools was used for collecting the data; characteristics of preterm neonates, preterm neonate's physiological conditions, and behaviour cues of preterm neonates checklist to assess signs of stability and signs of distress Results:  It was observed that the signs of preterm distress before receiving developmental care decreased directly after the program application and receiving developmental care, and then somewhat declined ten minutes later. A statistically significant difference was found between preterm behavior cues before implantation of developmental care, directly after receiving developmental care, and ten minutes later. Conclusion: Preterm neonates exhibited stable behavioral cues and fewer stress signs after application of the developmental supportive care. Recommendation: Proper pre-service and in-service training for newly recruited nurses and in-service training program for nurses about the most recent developmental supportive care interventions for preterm neonates to improve their performance about developmental supportive care to enhance preterm neonates behavior stability.