Nonbacterial thrombotic endocarditis (NBTE) is a rare condition that causes noninfectious vegetative lesions of heart valves. NBTE is generally seen in association with advanced malignancy. The patient in this case is a 54-year-old Caucasian male with a history of rate-controlled atrial fibrillation on rivaroxaban and morbid obesity post sleeve gastrectomy in 2021, who was admitted for atrial flutter. Transesophageal echocardiogram (TEE) cardioversion was planned due to difficulty in controlling the heart rate. During the procedure, cardioversion was aborted due to TEE findings of large mobile vegetation on the left atrial side of the posterior mitral valve leaflet. The patient was afebrile for the entirety of his 10-day hospital stay, and four sets of blood cultures were negative. Further workup with esophagogastroduodenoscopy (EGD) revealed a large partially obstructing ulcerated mass in the middle and lower third of the esophagus arising in the setting of Barrett’s esophagus which was biopsy positive for esophageal adenocarcinoma. The patient was found to have advanced malignancy with metastases to the liver, adrenal glands, and perirectal lymph nodes. This case emphasizes the utilization of a TEE prior to cardioversion and also highlights the importance of EGD prior to and post gastric sleeve surgery to evaluate for esophageal cancer.