With the efficacy of gene therapy verified in phase III trials, cancer patients will consider whether to accept gene therapy sooner or later. The purpose of this study is to investigate the attitudes of oncology physicians and nurses regarding effective gene therapy. A questionnaire was administered to 368 oncology physicians and nurses. A total of 328 valid questionnaires were returned (response rate, 89.1%). Gene therapy was considered as very safe or safe by 256 (78.0%) participants. Regardless of the stage of cancer, participants who advised patients to enroll in clinical trials and considered gene therapy as safe tended to accept the effective gene therapy. Gene therapy is considered to be a safe treatment. Most participants are willing to accept effective and verified gene therapy on the assumption that they themselves suffer from cancers.