Bronchioloalveolar carcinoma (BAC) is a distinct subtype of non-small cell lung cancer for which there is no optimal therapy for non-resectable or recurrent disease. This report describes a patient with BAC refractory to conventional chemotherapy but with a partial response to S-1, oral fluoropyrimidine, resulting in symptom improvement and weaning from oxygen supplementation. Our observation suggests that S-1 is a novel option for the treatment of advanced BAC.