This study was performed to describe the radiographic and ultrasonographic features of retained surgical gauze known as gossypiboma in 9 dogs. Female dogs (n = 8) were at higher risk and seven out of the eight cases had a history of ovariohysterectomy. Seven dogs were symptomatic and the most common clinical signs were vomiting, anorexia, and inertia. A palpable abdominal mass was detected in six dogs. Radiographic signs included a localized abdominal mass with soft tissue density (n = 7) or a mass containing speckled gas (n = 1). Ultrasonography showed a hypoechoic mass with a hyperechoic center (n = 4), or a homogeneous hypoechoic mass (n = 3). The remaining dogs (n = 2) showed an intestinal wall surrounding a hyperechoic center. Regardless of the characteristics of a mass, an acoustic shadowing was accompanied from the center of a mass in all dogs. Ultrasonography also revealed complications such as adhesion between a mass and adjacent organs, and peritonitis and intestinal obstruction around a mass. The gossypiboma can be considered when a hypoechoic mass accompanying a hyperechoic center with acoustic shadowing is observed on ultrasound examination.