Purpose: The aim of this study was to evaluate the dental anxiety levels of patients before periodontal surgery and to evaluate the effects of preoperative progressive relaxation exercises on vital signs and mouth opening. Materials and Methods: A total of 35 randomly selected patients who were scheduled for periodontal surgery were included in the cross-sectional study. Demographic data and a questionnaire including Corah Dental Anxiety Scale were applied before the surgery. Systolic and diastolic blood pressure, pulse and respiration including vital signs and mouth opening were measured. Then 30 minutes of relaxation exercise was performed. She was asked to take the position where she felt most comfortable and close her eyes. The environment is kept quiet. Thirty minutes of relaxation exercises were listened with a video headset and allowed to do the exercises. Vital signs and mouth opening were measured again after relaxation exercise. Results: 71.4% of the patients stated that dental treatment was not fearful, but the rate of dental anxiety before periodontal surgery was found to be 57.1%. Systolic blood pressure and mouth opening were significantly affected after relaxation exercise but no statistically significant change was observed in diastolic blood pressure, pulse and respiration measurements Conclusion: Progressive relaxation exercise applied before periodontal surgery has a myorelaxant activity in increasing the mouth opening and it is a cheap, painless, non-adverse non-pharmacological anxiolytic in reducing systolic blood pressure.