ABSTRACT Undifferentiated carcinoma of the pancreas is a malignant neoplasm that is uncommon among domestic species, especially cockatiels (Nymphicus hollandicus), one of the most popular birds kept as a pet throughout the world. The aim of this study was to describe the occurrence of an undifferentiated carcinoma in the pancreas of a cockatiel. A bird, an adult male that died naturally with swelling in the abdominal region, was referred to necropsy. Macroscopic examination showed poor body condition, the coelomic cavity filled with liquid and a white mass attached to the pancreas and other smaller masses attached to the duodenum. Tissue samples and organs were harvested and fixed in 10% buffered formalin, then routinely processed for histopathology and stained with hematoxylin and eosin. Microscopic analysis demonstrated an epithelial neoplasia with a predominantly solid pattern, lymphatic invasion and involvement of the intestinal serous membrane. These findings indicate the occurrence of an undifferentiated pancreatic carcinoma in a cockatiel that was diagnosed by histopathology.