Behçet's disease (BD) is a rare, multisystemic, chronic vasculitic disorder with unknown etiology. The most common signs of BD are recurrent aphthous oral ulcers, genital ulcers, ocular lesions, dermatological lesions, and arthritis. 1,2 BD may also affect the pulmonary and cardiovascular systems. 2-4 Frequency of BD is low but intracardiac thrombus (IcT) formation is even less common; this serious complication has been reported only as case reports. 5-7 Pulmonary artery aneurysm (PAA) is also very rare, and only a few pediatric patients have been reported in the literature. 6,7 IcT accompanying PAA is extremely rare in the pediatric age group. In this article, we present an unusual case of an adolescent patient with PAA and IcT who did not survive despite all medical therapies. CASE REPORT A 16-year-old male patient was admitted to the hospital with complaints of productive cough, fever, and chills. Despite oral amoxicillin/ clavulanic acid treatment, the patient's complaints increased; he developed shortness of breath and was admitted to another hospital. The patient had weight loss of 8 kg in the prior three months. Two years before admission, the patient was suspected to have BD because of recurrent anterior uveitis and treated with infliximab. The patient never developed oral or genital ulcers, arthralgia, or neurological complaints during follow-up. There was no family history of BD or consanguinity. A written informed consent was obtained from the parents of the patient.