Background: Preeclampsia had a negative effect on maternal and fetal outcomes; which considered as a life-threatening condition. Lifestyle modifications can reduce the complications of preeclampsia and improve its outcomes. Aim: To examine the effect of lifestyle modification guidelines onmaternal and fetal outcomes among pregnant women with mild preeclampsia.Subjects and method:  Design: A Quasi-experimental design was.  Setting: This study conducted at the antenatal outpatient unit in Port Said Maternity Hospital. Subjects: A purposive sampleof80 pregnant women with mild preeclampsia at above mentioned setting, they were assigned equally into two groups; the study group received lifestyle modification guidelines alongside the hospital protocol, while the control group received the hospital protocol only. Four tools were used for data collection, Structured Interviewing Sheet, Lifestyle Checklist, Maternal and Fetal Outcomes Assessment Sheet, and Proposed Lifestyle Modification Guidelines. Results: The lifestyle modification lowering the blood pressure, gestational weight gain, and proteinuria. Also, reducing the rate of maternal and fetal complications related to preeclampsia. Conclusion: Lifestyle modification in combination with pharmacological treatment are effective and safe protocol in modifying mild preeclampsia. Recommendations: Lifestyle modification guidelines are recommended to be included in the hospital protocol for the management of mild preeclampsia and may be added in maternal nursing curricula.