Background In this study, we aimed to evaluate the coronary sinus (CS) morphology with three-dimensional transthoracic echocardiography (3D-TTE) in patients with supraventricular tachycardia (SVT) who underwent electrophysiological study (EPS). Methods This cross-sectional study was conducted with 187 patients who underwent EPS between November 2016 and April 2017. Patients were divided into three groups: atrioventricular nodal reentrant tachycardia (AVNRT) (n = 72), non-AVNRT SVT (n = 58), and normal EPS (n = 57). All patients were evaluated with electrocardiography, TTE, and 3D-TTE. Results The CS diameter (CSD) and area (CSA) were found significantly lower in the normal EPS group than in the other groups. There was no significant difference in the CSD between AVNRT and non-AVNRT SVT groups. However, it was found that the CSA was significantly larger in the AVNRT group than in the non-AVNRT SVT group. In linear regression analysis, age and left atrial diameter were determined as independent predictor for CSD and CSA (P < 0.001 for each one). Conclusions The CSD and CSA assessed by 3D-TTE were different and dilated in the patients with SVT compared to those in the normal individuals. There was no significant difference in the CSD between the AVNRT and non-AVNRT SVT groups. However, the AVNRT group had a larger CSA than the non-AVNRT SVT group.