The purpose of this study was to clarify the effects of anxiety about dental treatment on pain during treatment. Subjects consisted of 57 consenting sixth-grade students at Tokyo Dental College (male: 32, female: 25), all of whom participated in this study during their clinical training program. They knew how third molars were extracted and all had experience of assisting in tooth extraction. Prior to the study, trait anxiety in the subjects was evaluated according to the State-Trait Anxiety Inventory (STAI, Japanese version). The students were asked to read one of two scenarios describing a scene in which a third molar was extracted while imagining themselves to be the patient. Scene 1 is set in an “environment where the patient feels safe and comfortable,” and the Scene 2 is set in an “environment where the patient feels strong anxiety”. The subjects were asked to imagine the anxiety and pain in that scenario and evaluate that pain according to a visual analogue scale (VAS). Two scenarios were randomly shown to the subjects in a crossover manner. No significant correlation between trait anxiety and preoperative anxiety was observed. There was no difference in level of preoperative anxiety for Scene 1 and Scene 2 between the high- and low-trait anxiety groups. This suggests that there was no relationship between sensitivity to anxiety as a characteristic of the subject and amplitude of anxiety immediately prior to treatment. Scene 2 elicited significantly higher anxiety before injection of regional anesthesia, significantly higher pain during insertion of the needle, and significantly higher pain during extraction of the tooth than Scene 1. This difference suggests that patients feel stronger pain if anxiety in the treatment environment is high and that it is, therefore, important to reduce anxiety during treatment to reduce pain.