Background: In Thailand, there has been no economic evaluation study of adjuvant chemotherapy for stage III colon cancer patients after resection. Objective: This study aims to evaluate the cost-utility of all chemotherapy regimens currently used in Thailand compared with the adjuvant 5-fluorouracil/leucovorin (5-FU/LV) plus capecitabine as the first-line therapy for metastatic disease in patients with stage III colon cancer after resection. Methods: A cost-utility analysis was performed to estimate the relevant lifetime costs and health outcomes of chemotherapy regimens based on a societal perspective using a Markov model. Results: The results suggested that the adjuvant 5-FU/LV plus capecitabine as the first-line therapy for metastatic disease would be the most cost–effective chemotherapy. Conclusions: The adjuvant FOLFOX and FOLFIRI as the first-line treatment for metastatic disease would be cost–effective with an incremental cost–effectiveness ratio of 299,365 Thai baht per QALY gained based on a societal perspective if both prices of FOLFOX and FOLFIRI were decreased by 40%.