Objective The influence of cancer boards with respect to the treatment decisions regarding chemotherapy remains to be elucidated. In the present study, we investigated the cases that presented at our institutional cancer boards, to assess the effect of cancer boards on the treatment decisions regarding chemotherapy. Methods Data from the cancer boards at Yamagata University Hospital, Yamagata, Japan, were collected. Along with data from the clinical records, the details of the discussions and the chosen plan of treatment of the cancer boards were analyzed. Results From February 2010 to February 2014, 1,541 cases were discussed at our cancer boards. Of these, 811 cases (52.6%) involved discussions about chemotherapy. Of those 811 cases, recommendations were made to alter the treatment plans for 189 cases (23.3%). The reasons for discouraging chemotherapy varied; however, 29/45 (64.4%) cases involved discouragement for the following reasons: old age, a comorbid condition, the physical (performance) status, or insufficient evidence to administer chemotherapy. Eighty-six patients were referred to the medical oncology department through the cancer boards. Conclusion Our results showed that cancer boards have a great influence on the treatment decisions regarding chemotherapy and the prompt referral of cases to medical oncologists as necessary. In terms of future research, we will evaluate the effect of cancer boards on the prognosis and outcomes of cases using the institutional cancer registry.