An HIV-1-infected adult presented with a short history of dyspnoea, productive cough and myalgia with fever. Shortly after presentation, he developed the abrupt onset of high-volume watery diarrhoea: stool culture grew Shigella sonnei. At the same time, he became hypoxaemic, and thoracic imaging showed bilateral lower lobe consolidation/collapse. Culture of sputum and blood was negative. The patient recovered with fluid resuscitation and ciprofloxacin monotherapy. This is the first reported case of pneumonia complicating S. sonnei dysentery in an HIV-infected adult.