Bone and soft tissue sarcomas are relatively difficult to treat or cure. Despite a multidisciplinary approach involving surgery, chemotherapy, and radiotherapy, metastatic or relapsed diseases are difficult to cure. Therefore, novel therapeutic options need to be explored. We investigated the use of peptide vaccination therapy for synovial sarcoma and osteosarcoma. The present trial for synovial sarcoma showed the safety, immunogenic properties, and partial clinical efficacy of peptides. However, the power of the vaccine, at least in the present trial, is not strong enough to suppress tumor growth in the presence of gross residual tumors. Therefore, the use of the vaccination therapy as an adjuvant to chemotherapy for the treatment of refractory tumors may be a promising tool.