Urinary bladder tumors are not common in guinea pigs, but case numbers being diagnosed have increased in the past years. The authors present 3 referred cases of primary urinary bladder tumors in pet guinea pigs diagnosed using diagnostic imaging (CT, radiography, and ultrasonography) and exploratory laparotomy. Excision was not possible in the first case as the tumor was located at the neck of the urinary bladder and the owner opted for intraoperative euthanasia. The second and third cases both had tumors originat…