Aims/hypothesis It is postulated that uptake rates for gestational diabetes mellitus (GDM) screening would be improved if offered in a setting more accessible to the patient. The aim of this study was to evaluate the proportion of uptake of GDM screening in the primary vs secondary care setting, and to qualitatively explore the providers' experiences of primary care screening provision.Methods This mixed methods study was composed of a quantitative unblinded parallel group randomised controlled trial and qualitative interview trial. The primary outcome was the proportion of uptake of screening in both the primary and secondary care settings. All pregnant women aged 18 years or over, with sufficient English and without a diagnosis or diabetes or GDM, who attended for their first antenatal appointment at one of three hospital sites along the Irish Atlantic seaboard were eligible for inclusion in this study. Seven hundred and eighty-one pregnant women were randomised using random permutated blocks to receive a 2 h 75 g OGTT in either a primary (n = 391) or secondary care (n = 390) setting. Semi-structured interviews were conducted with 13 primary care providers. Primary care providers who provided care to the population covered by the three hospital sites involved were eligible for inclusion.Results Statistically significant differences were found between the primary care (n = 391) and secondary care (n = 390) arms for uptake (52.7% vs 89.2%, respectively; effect size 36.5 percentage points, 95% CI 30.7, 42.4; p < 0.001), crossover (32.5% vs 2.3%, respectively; p < 0.001) and non-uptake (14.8% vs 8.5%, respectively; p = 0.005). There were no significant differences in uptake based on the presence of a practice nurse or the presence of multiple general practitioners in the primary care setting. There was evidence of significant relationship between probability of uptake of screening and age (p < 0.001). Primary care providers reported difficulties with the conduct of GDM screening, despite recognising that the community was the most appropriate location for screening.Conclusions/interpretation Currently, provision of GDM screening in primary care in Ireland, despite its acknowledged benefits, is unfeasible due to poor uptake rates, poor rates of primary care provider engagement and primary care provider concerns.