Acute mitral regurgitation (acute MR) is a rare cause of acute respiratory distress, which can present diagnostic challenges. We present the case of a 57 year old man who developed acute shortness of breath subsequently associated with fever, raised white cells and elevated CRP. Chest x-ray revealed unilateral shadowing and he was treated for pneumonia, despite the finding of severe mitral regurgitation on echo. Failure to respond to antibiotic treatment following 3 weeks on ITU led to the consideration of acute MR as the cause of his symptoms and he responded well to diuretics. He subsequently underwent mitral valve repair. The causes and clinical presentations of this condition are discussed.