Cardiac autonomic dysfunction assessed by the presence of arrhythmia, by the methods, such as heart rate variability or blood pressure variability, and by the electrocardiographic abnormalities is common in Guillain-Barr, syndrome (GBS). The goal of present study was to analyze the P-wave dispersion (PWD), which is the non-invasive marker of atrial arrhythmia, in GBS patients and to compare those with healthy individuals. Thirty-five patients with GBS (mean age 53.6 +/- 15.5 years) and 35 healthy controls (mean age 49.2 +/- 14.1 years) were included to this study. Demographic and clinical information of the patients with GBS were assessed retrospectively. A 12-lead surface electrocardiogram was acquired from all participants. Minimum and maximum P-wave duration and PWD were measured in the patients with GBS and healthy controls. Maximum P-wave duration and PWD were significantly longer, and minimum P-wave duration was significantly lower in the patients with GBS rather than the control group (p = 0.037, p < 0.001, p = 0.007, respectively). GBS disability scores were positively correlated with the maximum P-wave duration (p = 0.015, r = 0.406) and PWD (p = 0.001, r = 0.525). We found that PWD was significantly prolonged in GBS patients compared with the controls. The increased PWD which is cheap, quick, non-invasive and feasible electrocardiographic marker may be related to increased risk for atrial fibrillation in patients with GBS.