Sinus node disease (SND) is a leading indication for permanent pacemaker implantation and is classically attributed to age-related degenerative changes. Nevertheless, functional conditions may result in similar clinical and electrocardiographic presentations, particularly in atypical cases. Extra-cardiac thoracic masses causing cardiac compression are rare and often underrecognized. We report the case of a patient presenting with a tachycardia-bradycardia syndrome initially suggestive of SND, in whom a comprehensive etiological evaluation revealed an esophageal tumor causing significant left atrial compression. This unusual presentation highlights the importance of considering extracardiac structural abnormalities in the differential diagnosis of apparent sinus node dysfunction.