Purpose: We aimed to assess atrial conduction time and P wave dispersion in Gestational Diabetes Mellitus (GDM) patients. Methods: 30 patients with GDM and 30 healthy pregnant women were included to the study. Atrial conduction time times (PA) were calculated by the time interval from the onset of the P wave on the electrocardiography (ECG) to the onset of the late diastolic flow (Am wave) on echocardiography; from the lateral mitral annulus (PA lateral), septal mitral annulus (PA septum), and right ventricular tricuspid annulus (PA tricuspid). Results: Mean PWD were higher in GDM (52.7±5.1 ms vs. 28.9±4.2 ms, p<0.001). PA lateral, PA septal and PA tricuspid were significantly higher in the GDM patients compared to the control group (65.7±4.2ms vs. 47.7±4.7 ms, p<0.001; 56.1±3.4 ms vs. 40.8±3.7 ms, p<0.001 and 48.4±3.9 ms vs. 36.0±3.6 ms, p<0.001 respectively). Conclusion: We suggest that patients with GDM has higher PWD and higher atrial conduction and EMD times compared to otherwise healthy pregnant control group.