Background: Occurrence of right atrial masses, especially in patients with history of cardiac surgery, is rare. Differential diagnosis between malignant and non-malignant aetiologies might be cumbersome, and surgery is often required to prevent complications or disease evolution. Case: We report the case of a 16-year-old girl from a rural area of Sudan, who underwent surgery for a modified De Vega's tricuspid annuloplasty, and mitral and aortic valve replacement with mechanical prostheses. The patient was on regular follow-up but demonstrated a poor compliance to anticoagulation therapy with a time in therapeutic range between 52% and 20%. She remained asymptomatic, but a right atrial mass was diagnosed by transthoracic echocardiography during a follow-up visit 41 months after the first operation. Surgical removal of the mass revealed an organized thrombus arising from the point where the Prolene stitches for the tricuspid annuloplasty were previously passed. The patient recovered from surgery, was discharged home on post-operative day 10 and the first follow-up visit at 30 days after discharge confirmed a good clinical status and a normal transthoracic echocardiography (TTE). Conclusions: This case report describes the diagnostic and therapeutic work-out of a thrombus formation on the suture lines of a tricuspid annuloplasty. Moreover, it highlights the importance of a strict and long follow-up after valvular surgery and of the adherence to anticoagulation therapy, especially for patients living in rural areas of developing countries.