Mastoiditis is a known cause of cerebral venous thrombosis but rarely presents as an isolated laterals sinus thrombosis (LST) and venous infarct. We report an adult female patient who presented with chronic mastoiditis complicated by LST and venous infarct, documented by computerised tomography and magnetic resonance venography. This implicates mastoiditis as a potential and important cause of isolated LST and venous infarcts in brain.