Background Updated practice guidelines on adjuvant chemotherapy for completely resected colon cancer are lacking. In 2008, Cancer Care Ontario’s Program in Evidence-Based Care developed a guideline on adjuvant therapy for stages ii and iii colon cancer. With newer regimens being assessed in this patient population and older agents being either abandoned because of non-effectiveness or replaced by agents that are more efficacious, a full update of the original guideline was undertaken. Methods Literature searches (January 1987 to August 2015) of MEDLINE, EMBASE, and the Cochrane Library were conducted; in addition, abstracts from the American Society of Clinical Oncology, the European Society for Medical Oncology, and the European Cancer Congress were reviewed (the latter for January 2007 to August 2015). A practice guideline was drafted that was then scrutinized by internal and external reviewers whose comments were incorporated into the final guideline. Results Twenty-six unique reports of eighteen randomized controlled trials and thirteen unique reports of twelve meta-analyses or pooled analyses were included in the evidence base. The 5 recommendations developed included 3 for stage ii colon cancer and 2 for stage iii colon cancer. Conclusions Patients with completely resected stage iii colon cancer should be offered adjuvant 5-fluorouracil (5FU)–based chemotherapy with or without oxaliplatin (based on definitive data for improvements in survival and disease-free survival). Patients with resected stage ii colon cancer without “high-risk” features should not receive adjuvant chemotherapy. For patients with “high-risk” features, 5FU-based chemotherapy with or without oxaliplatin should be offered, although no clinical trials have been conducted to conclusively demonstrate the same benefits seen in stage iii colon cancer.