Thrombosis of the tricuspid valve is a very rare cardiac pathological condition, characterized by the location and formation of thrombus near the valve edges. Clinically it can be very easy to mistake it for a myxoma or an infective endocarditis. The aetiology of this condition is an alteration of coagulation, deep venous thrombosis, cardiac structural anomalies or idiopathic forms of hearts that appear structurally normal. From a clinical point of view, the thrombosis of the tricuspid, if it is not totally occlusive, causes the development of symptoms related to the reduced flow and to cardiac congestion: easy fatigue, distension of jugular veins, hepatomegaly and pulmonary congestion with dyspnoea and haemoptysis. The case we studied is of an unexpected death in a subject whose preliminary case history did not show any cardiovascular or pulmonary pathology. It was caused by a thrombosis in the tricuspid valve, originating from a deep venous thrombosis of right iliofemoral axis. In conclusion this case highlights the importance of defining precise anatomical abnormalities in forensic pathological cases.