To establish the sufficient therapy for elderly colorectal cancer patients, we retrospectively compared postoperative Tegafur/Uracil (UFT; Taiho Pharmaceutical Co., Ltd., Tokyo, Japan) and UFT plus protein-bound polysaccharide kureha (PSK) therapies in elderly patients with resected colorectal cancer. A total of 63 patients were collected; 39 patients were administered only with UFT (control group) and 24 patients were treated with UFT+PSK (PSK group). There were no differences in patient background, surgical outcomes, and drug compliance between the two groups. The 3-year relapse-free survival rate was 47.8% in the control group and 76.2% in the PSK group (p = 0.041). The 3-year overall survival (OS) rate was 52.8% in the control group and 80.8% in the PSK group (p = 0.0498). By subset analysis, in the patients whose tumor location was the colon (p = 0.016) and whose preoperative lymphocyte percentage was below 18.7% (p = 0.017), RFS was significantly better in the PSK group. Adverse drug reactions were rarely observed. All the adverse reactions were grade 2 or below, with no severe reactions. The present retrospective study suggests a possible efficacy of postoperative adjuvant therapy with UFT plus PSK in elderly patients over 70 years of age with resected colorectal cancer.