Introduction: Primary postpartum hemorrhage is one of the leading causes of maternal death in Bhutan but data on the incidence and risk factors for primary postpartum hemorrhage are scarce. The purpose of this research is to look into the incidence, its associated risk factors and maternal outcome of primary postpartum hemorrhage among women who gave birth at the national referral hospital. Methods: The incidence of primary postpartum hemorrhage was estimated total number of primary postpartum hemorrhage cases of total deliveries during the study period. A case-control study was conducted to identify risk factors for primary postpartum hemorrhage. Cases of primary postpartum hemorrhage was defined by blood loss of greater or equal to 500ml in vaginal delivery or greater or equal to 1000ml for abdominal delivery within 24 hours of delivery. A multivariable logistic regression was used to identify associated risk factors of primary postpartum hemorrhage. Results: Among 9,221 deliveries, primary postpartum hemorrhage occurred in 180 cases (1.95%; 95% CI=1.68%-2.26%) during two year period. The significant risk factors for primary postpartum hemorrhage were, labor induction (adjusted OR=2.27; 95% CI= 1.11-31.47, p=0.005), current pregnancy complications (aOR=2.50; 95% CI: 1.32-4.74, p=0.005), and gestational age at term delivery (aOR=6.49; 95% CI:1.12-37.48, p=0.037). The significant causes of primary postpartum hemorrhage were uterine atony (aOR=72.57; 95% CI:5.95-885.76, p=0.001), retained placenta (aOR=18.08; 95% CI:2.66-122.81, p=0.003) and perineal and cervical tear (aOR=27.80; 95% CI: 15.13-51.07, p less than 0.001). Conclusions: The incidence of primary postpartum hemorrhage was 1.95% which is lower compared to other South East Asian countries. The causes and risk factors identified in this study may help predict primary postpartum hemorrhage and aid healthcare providers in better management of primary postpartum hemorrhage in all women giving birth.