A four‐year‐old, castrated male ferret (Mustela putorius furo) was evaluated because of a one‐year history of sporadic cough. On physical examination a grade 5 of 6 holosystolic murmur was audible over the right apex of the heart. Radiographic findings included the presence of air bronchograms in apical lobes accompanied by pulmonary venous congestion. Colour Doppler echocardiography revealed a left‐to‐right shunting compatible with a ventricular septal defect. Medical therapy was initiated at the time of the diagnosis. The ferret was presented again 2 months after the initial examination for coughing and respiratory distress. Echocardiographic findings included tricuspid regurgitation, relative enlargement of left‐atrial diameter and decreased systolic function, with presence of pleural effusion. Thoracocentesis was performed and the therapeutic plan was revised. In the following months the symptoms did not recur. In the authors’ opinion this is the first report to describe the clinical findings of isolated ventricular septal defect in the ferret. Congenital heart defects are rare in this species, the present ferret being only the second case described.