Polycystic ovary syndrome (PCOS) is a common endocrine metabolic disorder in women of reproductive age. PCOS is often associated with insulin resistance and carries an increased risk of gestational diabetes mellitus (GDM). The aim of this study was to evaluate the risk of GDM in women with a history of PCOS. This was a retrospective cohort study conducted at a single center in Vietnam between January 2014 and December 2017. A total of 400 women who conceived through assisted reproductive technology (ART) were included, 200 who had been diagnosed with PCOS, and 200 without a PCOS diagnosis as controls. Multivariable logistic regression models were used to examine the association between risk of GDM and PCOS after adjusting for confounders. GDM was present in 37% of those with PCOS, compared with 26.5% in those without PCOS (RR 1.4, 95% CI 1.04–1.87, p=0.02). The prevalence of GDM did not differ significantly between PCOS phenotype groups (p=0.28). Women with PCOS undergoing ART had a higher risk of GDM after adjusting for differences in age, pre-pregnancy body mass index, type of infertility, ART indications, and type of ART (adjusted OR 2.04, 95% CI 1.06–3.92). First-trimester fasting plasma glucose (FPG) was also an independent predictor for GDM (adjusted OR 1.54, 95% CI 1.01–2.34). This study suggests that PCOS and first-trimester FPG are independent risk factors for the development of GDM.