Objective: There are many studies regarding the increased relationship between pregnancy outcomes and obstetrical complications of singleton with endometriosis such as preterm birth, preeclampsia, placenta previa, and small for gestational age. However, there was limited evidence of twin pregnancies with endometriosis. Thus, the objective of this study was to compare the pregnancy outcomes and obstetrical complications in twin pregnancies with endometriosis or without endometriosis in single institution. Methods: From January 2011 and July 2022, a cohort of twin pregnancies delivered in single institution was retrospectively analyzed. The patients who underwent surgical treatment before pregnancy and confirmed histologically; confirmed visually or histologically during cesarean section; in case of patients who underwent vaginal delivery, antenatal ultrasonographic findings showed typical ovarian endometriosis were included in endometriosis group. The pregnancy outcomes and obstetrical complications were compared between two groups. Results: In this study, a total of 1951 patients were examined. A total of endometriosis group was 143 (7.3%). Maternal body mass index was significantly lower in the endometriosis group (p<0.001). However, there were no significant differences in maternal age, mode of conception, and chorionicity between the endometriosis groups and the control group. There were also no significant differences in pregnancy outcomes: gestational age at delivery (p=0.619), the rate of delivery before 37weeks (p=0.728), and the mode of delivery (p=0.698). However, some obstetrical complications showed significantly higher rates in the endometriosis group: placenta previa (p=0.038), small for gestational age <10% (p=0.039), and postpartum hemorrhage (p=0.006). Logistic regression analyses were performed after adjusted for BMI showed patient with endometriosis had a higher risk of placenta previa (odds ratios (OR) 2.191, 95% confidence intervals (CI) 1.051-4.568), and postpartum hemorrhage (OR 2.506, 95% CI 1.444-4.348). After multivariable analyses, postpartum hemorrhage was significantly higher in patients with endometriosis (OR=2.264, 95% CI=1.265-4.054). Conclusion: Twin pregnancies with endometriosis had a significantly higher risk of postpartum hemorrhage. To confirm these outcomes, further large prospective study would be needed.