Malignant Ovine Theileriosis (MOT) caused by Theileria lestoquardi is considered a major constraint for sheep production in many areas of the world including Sudan. Pulmonary oedema is thought to be the main cause of animal death, but the mechanism, the cell types involved and/or the probable cause of this pneumonia has yet to be defined. The present study was carried out to investigate the pulmonary involvement post T. lestoquardi infection and to identify the cell types involved in pneumonia. Apparently healthy sheep were exposed to ticks challenge in T. lestoquardi endemic area. Lungs impression smears and tissue sections for histopathology were processed. At necropsy, fifteen infected sheep revealed severe pneumonia associated with oedema and accumulation of creamy-grayish frothy exudates. The microscopic findings of examined lungs showed emphysema, congestion, collapse and proliferation of immense amount of different kinds of cells. The current study indicates that T. lestoquardi infections are accompanied with remarkable pulmonary involvements and may lead to respiratory failure and death.