Patients with a septate uterus often have endometriosis, which can exacerbate their adverse pregnancy outcomes. We aimed to describe the clinical characteristics and treatment outcomes of patients with a septate uterus complicated by endometriosis.This retrospective study included patients who had a septate uterus complicated by endometriosis and were treated in Wuhan Tongji Hospital in the past 10 years. The characteristics of patients with a septate uterus and endometriosis were collected and described in terms of their preoperative and postoperative pregnancy outcomes.There were 24 cases with a complete septate uterus and 49 cases with an incomplete septate uterus.Combinations of other malformations are more common in patients with complete septate uterus. In patients with a septate uterus, endometriosis often affected the ovaries, most commonly the left side (P < 0.001). Non-significant difference in the staging of endometriosis between complete and incomplete septate uterus (P= 0.812). Surgical treatment greatly improved the reproductive function and increased the live birth rate of patients with a septate uterus complicated by endometriosis (P < 0.001).Compared to a septate uterus uncomplicated endometriosis, a septate uterus complicated by endometriosis significantly affects reproductive function. Surgical treatment can significantly improve the pregnancy outcomes of patients with a septate uterus and endometriosis. Clinicians should pay attention to timely diagnosing and treating these patients.Copyright © 2024. Published by Elsevier Masson SAS.