Ultrasonographic features of canine abdominal malignant histiocytosis (MH) of 16 dogs are reported. The most common finding was the presence of hypoechoic nodules in the spleen, some of which caused distortion of the splenic margin. The liver was the second-most commonly affected organ. Hepatic ultrasonographic features were highly variable, including hypoechoic, hyperechoic, or mixed echogenic lesions. Other common ultrasonographic abnormalities included hypoechoic nodules in the kidneys and mesenteric and medial iliac lymphadenopathy. The results of this study suggest that the ultrasonographic appearance of canine abdominal MH is nonspecific, and definitive diagnosis requires cytologic or histologic examination.