OBJECTIVE Perioperative oral health care can prevent postoperative complications, but it is also important to maintain oral health afterward to avoid later adverse events. This study examined (a) the relationship between knowledge and attitude toward oral health (KAOH) and oral/periodontal status (OPS) in patients receiving surgery, and (b) the changes in KAOH by perioperative oral health care and education. METHODS Patients receiving surgery who visited our hospital's dental clinic beforehand were prospectively recruited. All participants received oral health care and education. In questionnaires assessing KAOH before and after surgery, respondent answers were generally classified as positive or negative. OPS was assessed before surgery. Associations between KAOH and OPS and perioperative changes in KAOH were statistically tested. RESULTS A total of 507 patients answered the questionnaire before surgery, among whom 324 patients also completed it afterward. Preoperative OPS was significantly worse in the negative than in the positive KAOH group. Positive answers for KAOH increased significantly from 68.6% to 92.2% during the perioperative period. CONCLUSIONS We found that patients with poor KAOH also had poor OPS, but KAOH could be improved by perioperative oral health care and education, suggesting that perioperative oral health management could improve oral health knowledge and attitudes.