Background: preeclampsia is a pregnancy-associated multisystem disorder that affects 3-5% of all pregnancies . It remains a leading cause of maternal and neonatal morbidity and mortality in the world . Magnesium sulphate is the drug of choice in the management of impending eclampsia and eclampsia. Magnesium sulphate has an anticoagulating effect, which has been used early in preeclampsia to delay the advance of the disease . This action however, is considered as a disadvantage, because it can prolong the bleeding time.The prolongation of bleeding time may preceipitate postpartum haemorrhage. Objective: the objective of this study was to observe the effects of magnesium sulphate on bleeding time in patients with preeclampsia. Patients and Methods: a study was conducted between April 2018 and February 2019. Fiffty patients with preeclampsia were included in the study. Bleeding time was measured through modified Ivy method. These measures were recorded before, immediately and 24 hours after discontinuation of magnesium sulphate. Results: after magnesium sulphate therapy; bleeding time is increased , haemoglobin level and haematocrit level are decreased. Conclusion: bleeding time in patients with severe preeclampsia was prolonged with magnesium sulphate infusion This is clinically important because it worsens the present conition and causes possible complications.