Health education is considered the backbone of health care management predominantly with diabetic patients. In order to minimize oral health problems within this group, especially those complaining of gingivitis, nurses must be well trained in assessing the educational needs of patients regarding their oral health status. Health education about oral hygiene with pharmacological and non pharmacological agents or herbal products is considered a total management in several cases. Green tea has several benefits for oral health. It limits enzymatic changes and acts as an antimicrobial, anti-inflammatory and deodorant agent. As an herbal product, green tea is accessible, effective and safe for diabetics with gingivitis. This is a quasi-experimental study aimed at determining the effect of health education about oral care with green tea powder on diabetics' oral health knowledge, skills and gingivitis' status. The study was conducted at the three medical sections of Gamal Abd El Nasser Hospital in Alexandria, Egypt. The sample was comprised of sixty adult diabetics who were selected by convenient sampling technique according to specific inclusion criteria. Patients were randomly divided into study and control groups, thirty in each. The Oral Health Education Assessment Questionnaire (OHEAQ) was used to determine the knowledge and skills of adult diabetics regarding oral health care and associated green tea benefits. The Gingival Evaluation Interview Sheet (GEIS) was used to assess gingivitis severity and its manifestations. Results revealed that there was a statistically significant difference between the study and control groups after the first and second assessments of educational intervention with green tea powder, in relation to perceived oral health care knowledge and practices with green tea, gingival inflammation severity scores, and gingivitis manifestation scores. All of these variables were improved in favor of the study group. In conclusion, oral health education with herbs and particularly green tea is an admirable nursing intervention to improve patients' oral health literacy and oral self-care practices for adult diabetic patients with gingivitis.