Objectives We sought to assess the prevalence of gestational trophoblastic diseases (GTD) among pregnant women at Sultan Qaboos University Hospital (SQUH) and compare our results with the international studies. We also sought to determine the risk factors, histological features, sonographic findings, and outcomes in women with GTD. Methods We conducted a retrospective cohort study of all women diagnosed with GTD and followed at SQUH between November 2007 and October 2015. We collected data on maternal demographics, risk factors, sonographic features, histological diagnosis, follow-up period, and chemotherapy treatment from the hospital information system. Results Sixty-four women with GTD were included in the study with a mean age of 31.0±7.5 years, mean gravidity 4.0, and parity 2.0. The prevalence of GTD was 0.3% (one in 386 births), and the most common risk factors were increased maternal age and multiparity. A partial hydatidiform mole was diagnosed in 54.7%, complete hydatidiform mole in 43.8%, and invasive mole in 1.6% of women. Eleven percent of women required chemotherapy. Typical ultrasound features for partial molar pregnancy were present in 54.7% of our sample, while snowstorm appearance was seen in 89.3% of those with complete mole. Negative beta-human chorionic gonadotropin was achieved 70 days after diagnosis in 41 women. Conclusions The awareness of the risks and complications of GTD among physicians with close follow-up is paramount. There is a need to establish a national registry of GTD cases in Oman.