Abstract. A 1-month-old Domestic Shorthair kitten was submitted for autopsy, with a history of upper respiratory tract infection and diarrhea. This was the third kitten from the same litter that had died with similar clinical findings within a period of 1 month. Severe conjunctivitis, rhinitis, tracheitis, and bronchointerstitial pneumonia were present, together with lymphohistiocytic colitis. Respiratory lesions were caused by infection with Felid herpesvirus 1. Colonic lesions were associated with the presence of long filamentous bacteria, identified as Clostridium piliforme, in the cytoplasm of epithelial cells. Our report describes a case of concurrent C. piliforme infection (Tyzzer's disease) and feline rhinotracheitis in a kitten.