The rate of soft tissue metastases and the importance of abdominal ultrasonography in initial staging of canine skeletal osteosarcoma (OSA) are not known. The purpose of this study was to determine whether abdominal ultrasonography should be performed routinely at initial diagnosis of skeletal OSA or if certain abnormal physical examination or diagnostic findings would provide greater indication to perform ultrasonography. Eighty dogs with OSA that had an abdominal ultrasonogram performed at diagnosis were included. Abnormal findings were present in 36 of 80 dogs. Twenty-three abnormalities were evaluated with either fine-needle aspirate or biopsy and 19 were benign. None of the ultrasonograms revealed abdominal OSA metastases; however, 4 of the 80 ultrasonograms (5%) revealed another primary neoplasia. Further, 2 of the 9 cases that received an ultrasonogram due to a palpable abdominal mass were diagnosed with another primary neoplasia compared with only 1 of the 49 cases that received an ultrasonogram for routine staging. Abdominal ultrasonography as a part of staging is unlikely to reveal metastases from OSA and may not be a useful routine staging tool; however, in certain populations of dogs, such as those with palpable abdominal masses, abdominal ultrasonography may reveal abnormalities that may influence treatment decisions.