An insulinoma was diagnosed in an eight-year-old, male golden retriever. Four fasted serum glucose concentrations were within the reference values over a seven-week period. Two serum fructosamine values over the same seven-week period were both low. An exploratory laparotomy and histopathology of an excised pancreatic nodule confirmed the diagnosis of insulinoma. This report demonstrates that a dog with a histologically confirmed insulinoma can have normal fasting serum glucose concentrations on multiple assays. It also demonstrates that fructosamine assays may be helpful in the diagnostic evaluation of normoglycaemic dogs with clinical signs suggestive of insulinoma.