A three-year-old male Labrador retriever was presented at the Clinic of Internal Medicine, University of Zagreb, Croatia. The owner reported that the dog was ataxic, and this was evident by its markedly unsteady, swaying gait. The dog also had difficulty rising and fell several times while trying to stand. It had come into contact with the explosive, pentaerythrityl tetranitrate, while training to detect explosives. The following clinical symptoms were observed: bradycardia, depression, mild disorientation and a broad-based stance. The dog had conscious proprioceptive deficits in the hindlimbs, but cranial nerve function was normal except for miosis. Ion scan analysis of the dog's serum after evaporation of the current phase by mass spectroscopy revealed the presence of fragments that are characteristic of pentaerythrityl tetranitrate. The aim of the present case report was to identify pentaerythrityl tetranitrate poisoning and describe the clinical signs of pentaerythrityl tetranitrate poisoning in dogs. To the authors' knowledge, there are no published scientific articles on pentaerythrityl tetranitrate poisoning in dogs.