Background: Breast milk odor is considered one of the updated developmental care used for stabilizing vital signs and decreasing distressed behaviors of preterm newborns. The present study aimed to evaluate the effect of continuous olfactory stimulation using breast milk on physiological indices and behavioral responses of preterm neonates. Research design: quasi experimental design was utilized. Setting: It was conducted at Neonatal Intensive Care Unit of EL Menshawy Hospital. Subjects: purposive sample of 60 premature neonates who were randomly divided into two groups; study group as breast milk olfactory stimulation and control group. The study tools: Assessment of Preterm Neonates Structured Interview Schedule, Preterm Neonate's Physiological Indices and Neonate's Behavioral State Assessment Scales were used for data collection. Results: there were statistically significant difference among control and study groups regarding physiological indices and behavioral responses of premature neonates pre and post intervention. Conclusion: stimulation with breast milk smell improves physiological parameters and behaviors of preterm hospitalized newborns. Recommendations: breast milk olfactory stimulation should be applied as a routine supportive care for all premature neonates at Neonatal Intensive Care Units.