A 13-year-old Thoroughbred gelding presented to Cornell University’s Equine and Nemo Farm Animal Hospital with a three-month history of decreased appetite and lethargy followed by tachycardia, intermittent fever, weight loss, weakness, reluctance to move, and increased respiratory effort. On presentation, he was alert and responsive but quiet, with poor body condition (BCS 2/9) and generalized weakness. He presented with a severely increased respiratory rate and effort, tachycardia and hyperthermia. On thoracic auscultation bilateral loud, harsh lung sounds with crackles caudodorsally and dull sounds cranioventrally were detected. Ultrasound showed diffuse severe comet tailing artifacts and a thickened pleura bilaterally along with small nodules on the left, areas of increased echogenicity on the right with a consolidated cranioventral lobe. Blood work revealed a severe inflammatory response and anemia of chronic disease. Based on history, physical exam and ultrasound findings a presumptive diagnosis of Equine Multinodular Pulmonary Fibrosis (EMPF) was made. Radiographs, bronchoalveolar lavage, Equine Herpes Virus-5 PCR, and lung biopsy confirmed this diagnosis. Treatment was continued for a week, and on day 8, the horse started to decline. After developing a secondary bacterial pleuropneumonia he was euthanized. Findings on necropsy supported the diagnosis of EMPF and a secondary bacterial infection.