<b><i>Purpose:</i></b> The aim of this study was to investigate the oncologic impact of preoperative or postoperative chemoradiotherapy on stage IV rectal cancer. <b><i>Methods:</i></b> A total of 140 consecutive patients with locally advanced mid-to-lower rectal cancer and resectable stage IV disease were prospectively enrolled. In total, 69 patients received chemoradiotherapy (26 preoperatively and 43 postoperatively); in contrast, 71 did not. Survival curves were constructed using the Kaplan-Meier method, and a multivariate analysis was performed to identify independent prognostic factors. <b><i>Results:</i></b> According to the multivariate analysis, radiation therapy was not an independent factor associated with either survival or recurrence. The overall survival curves revealed that patients who underwent radiotherapy tended to have a better survival compared with patients who did not undergo radiotherapy; however, this trend was not statistically significant (p = 0.057). The disease-free, local recurrence-free, and distant metastasis-free survival curves did not differ significantly between the two groups. The local recurrence-free survival rates for patients who underwent preoperative radiotherapy were significantly higher than those for patients who underwent postoperative radiotherapy (p = 0.042). <b><i>Conclusion:</i></b> Preoperative radiotherapy, rather than postoperative radiotherapy, may improve local control of stage IV rectal cancer. However, chemoradiotherapy did not improve the survival of patients with stage IV rectal cancer in this study.