Background Mothers of infants hospitalized in the Neonatal Intensive Care Unit (NICU) may experience a variety of psychological problems such as anxiety, depression, and stress. Purpose: To evaluate the effect of supportive nursing intervention on maternal stress and selected neonatal outcomes. Sampling: A purposive sample of 100 high risk pregnant women and 86 neonates was included. Design: A quasi experimental design was utilized. Setting: The study was conducted at Obstetrics and Gynecology departments and neonatal intensive care units in Menoufia University Hospital and Shebin El-Koom Teaching Hospital. Instruments: Three instruments were used. Instrument one: structured interview questionnaire sheet. Instrument two: parental stressor scale (PSS): NICU. Instrument three: Astrid Lindgren Children's Hospital pain scale for neonates (ALPS-Neo). Results:  Mean of maternal stresses was lower in the study group on time 2 and time 3 than on time 1 as follows (61.30±6.44, 64.85±6.17, and 95.94±7.55 consequently). Therefore, there were very highly statistical significant differences at 1‰ level of statistical significance. Furthermore, on posttest neonates in the study group exhibited fewer levels of pain, higher weight gain and fewer days of hospitalization than neonates in the control group. Conclusion: Implementation of supportive nursing intervention reduced maternal stress, contributed to more increase in neonates' weight and shorter duration of hospitalization on posttest than neonates in the control group.  Recommendations: It was recommended that continuous in-service education programs should be developed and implemented in all Obstetrics and NICUs to improve quality of care provided for high risk pregnant mothers and their preterm neonates.