Abstract Introduction Crista terminalis is a fibromuscular ridge at the posterolateral region of the right atrium (RA). Prominent crista terminalis can mimic pathologic RA mass on transthoracic echocardiograms. Transesophageal echocardiography can be used to differentiate non pathologic structures from pathologic ones. Case Report A 51–year–old men was referred to our clinic with typical atrial flutter. Transthoracic echocardiogram (TTE) revealed a RA mass. It was round, 15 mm in diameter, immobile, not calcified, and located at the posterior region of RA. Transesophageal echocardiography (TEE) showed prominent crista terminalis superiorly located beneath superior vena cava in the RA at 91 degrees midesophageal position. The patient undergoes catheter ablation for typical atrial flutter. Discussion Several congenital structures and normal variants such as Chiari’s network, eustachian and thebesian valves, and atrial septal aneurysms may simulate pathologic RA masses such as RA thrombus or myxomas. However, in this case, an anatomical variant is associated with an arrhythmia that requires treatment. Conclusion In this case we want to emphasize that prominent crista terminalis can mimic RA mass and may lead to atrial arrhythmias. TEE can be used to differentiate normal structures from pathologic.