A case of gallbladder agenesis associated with Gilbert's syndrome in a 52-year-old man with a striking family history of cholelithiasis is reported. The diagnosis of Gilbert's syndrome was made 30 years earlier, whereas the anomaly of the gallbladder was manifested when the patient, at the age of 34 years, started complaining of abdominal symptoms suggestive of biliary tract disease. Diagnostic confirmation was accomplished by magnetic resonance cholangiography, thus avoiding laparotomy, whereas conventional hepatobiliary imaging studies and laparoscopy could not achieve a definite diagnosis. No other malformations were detected. To our knowledge, this is the first report of an association between gallbladder agenesis and Gilbert's syndrome. Such association may be incidental or could represent the occurrence of a concomitant metabolic error in adults with isolated agenesis of the gallbladder.