A 2.5-year-old female guinea pig (Cavia porcellus) presented for reduced appetite, signs of abdominal pain, increased respiratory effort, and a distended abdomen. Cholelithiasis was diagnosed by radiography and ultrasonography. The cholelith was surgically removed using cholecystectomy. After surgery the animal recovered quickly and clinical signs resolved. Stone analysis revealed a composition of 20% weddellite (calcium oxalate dehydrate) and 80% apatite (calcium phosphate). Histologic examination of the gallbladder revealed no significant pathologic changes. Three months after the surgical procedure the patient continued to do well and diagnostic imaging revealed no abnormalities. Surgical therapy was straightforward and effective.