Background: Breast engorgement can cause considerable discomfort for mothers and hinder successful breastfeeding. This can lead to early discontinuation of breastfeeding, and dangerous medical conditions. Olive oil is one of the non-pharmacological methods used for treating breast engorgement. Aim of the study: explore the effect of olive oil massage on breast engorgement and breastfeeding among primiparous postnatal mothers with cesarean section delivery. Design: A quasi-experimental research design was adopted. Setting: the study was carried out at the maternity outpatient clinics of Damanhour General Hospital in El-Beheira Governorate, Egypt. Subjects: A purposive sample of 80 postpartum women with breast engorgement was selected and classified into two equal groups of 40, study and control. Data collection tools: three tools were utilized for data collection; tool one: basic data structured interview schedule, which included socio-demographic data and breastfeeding history; tool two: breast engorgement assessment scale, which involved Modified Reeda Scale, Visual Analog Scale, Newton's Scale and Pyrexia Chart; tool three: Latch on scale. Results: this study revealed that severe breast engorgement highly significantly fell steadily from 27.5% to 0% among the study group, whereas it reduced slightly from 20 % to 17.5% among the control group. Successful breastfeeding was also highly significantly elevated sharply from 7.5% to 92.5% among the study group, while it remained the same (15%) among the control one. Conclusion: this study concluded that olive oil breast massage significantly relieved breast engorgement and enhanced successful breastfeeding. Recommendations: Olive oil breast massage could be utilized as an independent nursing intervention to reduce breast engorgement.