Intraoperative ultrasonography (IOUS) is used in medicine for diagnosis and guidance during oncologic surgery. The aims of this study were to assess the performance, feasibility, advantages and difficulties of the IOUS technique in dogs with suspected intra-abdominal tumors. The study included nine client-owed dogs that had suspected intra-abdominal tumors (spleen, liver or bowel) based on transabdominal ultrasound examination and that were subsequently referred for exploratory laparotomy surgery. During surgery, IOUS was performed; results of preoperative transabdominal ultrasonography, inspection by the surgeon and IOUS were compared on a case-by-case basis. IOUS was helpful in determining lesion resection in all cases. Lesions detected solely by the use of IOUS were observed in seven out of nine cases. Analysis of these cases demonstrated that IOUS can be a tool to assist during oncology surgery on the liver, spleen or bowel. Dogs with hepatic tumors can have small non-palpable intraparenchymal nodules, which may be visible by IOUS.