Penile Mondor's disease (PMD), or thrombosis of the dorsal vein, is an under-reported benign condition. Its aetiology is poorly understood. Clinically, it presents as a palpable cord in the dorsal vein of the penis, with pain or local discomfort, especially during erection. PMD may be diagnosed based on the medical history and physical examination. Management of the condition is conservative, with practitioners opting for various strategies including sexual/masturbatory abstinence, localised anticoagulant topical therapy and oral nonsteroidal anti-inflammatory drugs. In many cases, PMD will resolve within 4-8 weeks of presentation. Thrombectomy and resection of the superficial penile vein are applied surgically in patients refractory to the medical treatment. We describe the case of a 33-year-old patient known to have HIV who presented for severe painful dorsal induration and swelling of the proximal third of the penis. The patient had no recent history of sexual intercourse, penile trauma or other well-known risk factors for PMD. The physical examination was unequivocal, so a Doppler ultrasound was performed. A diagnosis of PMD was made and conservative treatment was prescribed. During a follow-up visit after 6 weeks, the patient had no symptoms and physical examination did not reveal anything pathological.