Clinical guidelines urge timely postpartum screening for diabetes among women with gestational diabetes mellitus (GDM), yet patient factors associated with screening uptake remain unclear. We aimed to identify patient factors associated with completed postpartum diabetes screening (2-hour oral glucose tolerance test within 4-12 weeks postpartum), as recommended by the American Diabetes Association (ADA). Within the context of Gestational Diabetes’ Effects on Moms (GEM), a pragmatic cluster randomized trial (2011-2012), we examined survey and electronic health record data to assess clinical and sociodemographic factors associated with uptake of ADA-recommended postpartum screening. Participants included 1642 women (76% racial/ethnic minorities) identified with GDM according to the Carpenter and Coustan criteria in a health system that deploys population-level strategies to promote screening. To contextualize these analyses, screening rates derived from the GEM trial were compared with those in the health system overall using registry data from a concurrent 10-year period (2007-2016, n=21 974). Overall 52% (n=857) completed recommended postpartum screening in the analytic sample, comparable to 45.7% (n=10 040) in the registry. Screening in the analytic sample was less likely among women at elevated risk for type 2 diabetes, assessed using items from an ADA risk test (vs non-elevated; adjusted rate ratio (aRR)=0.86 (95% CI 0.75 to 0.98)); perinatal depression (0.88 (0.79 to 0.98)); preterm delivery (0.84 (0.72 to 0.98)); parity ≥2 children (vs 0; 0.80 (0.69 to 0.93)); or less than college education (0.79 (0.72 to 0.86)). Screening was more likely among Chinese Americans (vs White; 1.31 (1.15 to 1.49)); women who attended a routine postpartum visit (5.28 (2.99 to 9.32)); or women who recalled receiving healthcare provider advice about screening (1.31 (1.03 to 1.67)). Guideline-recommended postpartum diabetes screening varied by patient clinical and sociodemographic factors. Findings have implications for developing future strategies to improve postpartum care.