We report a patient with gallbladder cancer and multiple liver and lymph node metastases which completely responded to S-1, an oral fluoropyrimidine anticancer drug. The patient was enrolled in the "Late phase II study of S-1 in patients with advanced biliary tract cancer". A partial response was confirmed after the first two courses of S-1 monotherapy, and anti-tumor efficacy was finally evaluated as a complete response after the 5th course. S-1 was discontinued after the 18th course because of long CR, and the patient has been alive and disease-free for more than 3 years. Grade 2 anorexia, diarrhea, hand-foot skin reaction, and tasty disturbance were observed, but no grade 3 or more toxicities were noted. S-1 appeared to be effective against advanced gallbladder cancer and showed excellent tolerability.