OBJECTIVE To evaluate the obstetrical and oncological progression of twin pregnancies with hydatidiform mole coexisting fetus (HMCF). METHODS Using a retrospective method based on patients from the Women's Hospital, Zhejiang University School of Medicine database between January 1990 and October 2020, 17 patients were histologically confirmed as having HMCF, and the patients' prenatal diagnosis, outcomes and development of gestational trophoblastic neoplasia (GTN) were reviewed. RESULTS Among these 17 cases, 11 (64.71%) cases were complete hydatidiform mole coexisting fetus (CHMCF), and 6 (35.29%) cases were partial hydatidiform mole coexisting fetus (PHMCF). The gestational age at diagnosis of CHMCF was significantly earlier than that of PHMCF [9 (8-24) vs. 18 (11-32) weeks, respectively, P < 0.05]. The live birth rate of PHMCF was slightly higher than that of CHMCF (33.33%; 18.18%), but this difference was not statistically significant. The overall rate of GTN incidence of HMCF was 47.06% (8/17), and the GTN rates of PHMCF and CHMCF were 33.33% (2/6) and 54.55% (6/11), respectively. There was no significant difference in the GTN rate between patients who chose to continue pregnancy and those who terminated pregnancy before 24 weeks of gestation. The GTN rate of patients with term delivery was not significantly higher than that of preterm delivery. CONCLUSIONS In HMCF cases, the incidence rate of CHMCF was higher than that of PHMCF, and PHMCF is more difficult to diagnose in the early stage. Continuing pregnancy does not increase the risk of GTN compared to terminating pregnancy. In cases of HMCF, when the fetal karyotype is normal and maternal complications are controlled, it is safe to continue the pregnancy and extend it to term.