In mammals, circulating blood volume increases during late pregnancy, which adds to the volume load on the heart. In humans, this physiological change increases the risk of heart failure. Similar hemodynamic changes have been reported in cats during late pregnancy. This report describes the first known case of medically managed heart failure in a cat during late pregnancy, resulting in successful natural delivery. A 3-year-old pregnant Russian Blue cat presented with acute respiratory distress. Thoracic radiography and echocardiography revealed cardiomegaly and a pleural effusion. Due to constraints on the part of the owner, hospitalization was not feasible. Pimobendan, a drug with positive inotropic and vasodilatory effects, was administered to improve cardiac output. The respiratory symptoms resolved quickly, and the cat spontaneously delivered of three kittens occurred on day five. Postpartum follow-up showed no recurrence of symptoms, and the cardiac parameters had improved. Echocardiography and the clinical course revealed no underlying heart disease, suggesting that the heart failure occurred due to a physiological increase in blood volume during late pregnancy. This case demonstrates that cats without a history of heart disease may be at risk of developing peripartum heart failure. While the safety of pimobendan in pregnant cats remains unclear, this outcome indicates that it could be an effective treatment for managing heart failure during late pregnancy.