Limited information is available on the ultrasonographic characteristics of extruded gallbladder mucoceles. The objective of this retrospective case series study was to describe the ultrasonographic features of extruded gallbladder mucoceles in a group of dogs. Medical records of four veterinary centers were searched between June 2010 and January 2018 for all dogs with a suspected extruded gallbladder mucocele based on abdominal ultrasound. Seven client-owned dogs met the inclusion criteria. All seven dogs had a discrete, heteroechoic, multilayered, stellate, or striated mass within the peritoneal cavity. Blood flow was not present in these structures. Four of these structures were identified in the caudal abdomen. In five cases, the gallbladder lumen was filled with material similar in appearance to the free-floating peritoneal mass. Four cases were confirmed surgically and one case was confirmed at necropsy. Histopathology of the gallbladder wall was evaluated in all surgical cases and analysis of the free-floating material was performed in one of the four cases. Extruded gallbladder mucoceles have common imaging characteristics that may be helpful in establishing a presumptive diagnosis. Additionally, these structures may have extensive migratory capacity. The results of the study justify the recommendation for exploration of the entire abdomen during cholecystectomy for gallbladder mucocele removal.