In the international literature, the most commonly recommended intervention for managing oral mucositis is good oral care, assuming that nurses have sufficient knowledge and skills to perform oral care correctly. The aim of the present study was to investigate if knowledge and skills about oral care improve when education in oral care is provided to nurses in charge of patients who are at risk of oral mucositis. This intervention study consists of a baseline test on the knowledge and skills of nurses of the haematology wards of two different hospitals. Oral care education sessions were given in one hospital and follow-up tests were performed in both hospitals. Nursing records were examined and observations of nurses performing oral care were made at baseline as well as at follow-up. The results show significant differences in the scores for knowledge and skills before and after the education, whereas there was no difference in scores at the two points in time for the comparison hospital, where no education had taken place. The records test showed no differences at baseline or follow-up for the two groups. Observations showed that nurses who followed the education session implemented the oral care protocol considerably better than those who did not attended. Education in oral care has a positive influence on the knowledge and skills of nurses who care for patient at risk of oral mucositis, but not on the quality of oral care documentation.