Pulmonary oedema of uncertain aetiology is a diagnostic challenge to clinicians worldwide. Many indicators are proposed to differentiate between cardiogenic and non-cardiogenic pulmonary oedema. Mixed pulmonary oedema is an overlap between high hydrostatic pressure and increased permeability at the microvascular level. In our case, a 77-year-old patient presented with a nine-day history of shortness of breath. He was hypoxemic in the emergency department, had a pan-systolic murmur on auscultation, and blood results showed raised inflammatory markers without any fever. His chest X-ray and computed tomography pulmonary angiogram showed asymmetric pulmonary oedema in bilateral superior lobes and bilateral pleural effusions. Point-of-care echocardiography revealed severe mitral regurgitation. Transoesophageal echocardiography confirmed mitral valve prolapse with the chordae rupture and systolic vein reversal flow seen in the right superior pulmonary vein. He was treated with antibiotics and diuretics. After starting intravenous diuretics, there was a rapid symptomatic improvement, and a repeat chest X-ray showed significant improvements. We concluded that it was a case of mixed pulmonary oedema with predominant cardiac aetiology, and he was referred to cardiothoracic surgery for mitral valve replacement. The case showed that mixed pulmonary oedema with atypical chest radiography appearances would be a diagnostic challenge for clinicians. In such presentations, both cardiogenic and non-cariogenic causes of pulmonary oedema should be considered.