OBJECTIVE Patients requiring endodontic treatment often experience high levels of anxiety. The aim of this research is to investigate the effect of oral administration of lavender on the anxiety score of these patients. METHODS In this double-blinded randomized clinical trial conducted in 2021, 64 patients with symptomatic irreversible pulpitis were recruited using a simple random sampling technique. Blinding was achieved for both the patients and the evaluators. The samples were split into intervention and control groups using a table of random integers to randomize them. An hour before the commencement of the procedure, the patients filled out the dental anxiety questionnaire. Twenty drops of water in 250 ml of water were given to the control group, whereas 20 drops of lavender extract added to 250 ml of water were given to the intervention group. Two groups completed the anxiety questionnaire 60 minutes after ingesting the remedies. To analyse the data, paired and independent t-tests, and multiple regression analysis were used. RESULTS 64 patients were randomized and analyzed. Thirty-two of them who were in the control group experienced a substantially smaller decrease in their dental anxiety score compared to those 32 patients who were in the control group (p=0.001). This difference persisted even after grouping individuals by age, sex, and weight. CONCLUSIONS The administration of oral lavender extract drops to individuals requiring endodontic treatment appeared to significantly reduce their dental anxiety scores. The research registration number in the Iranian Registry of Clinical Trials is IRCT20120908010773N2, which is available at https: //irct.behdasht.gov.ir/. (EEJ-2024-03-50).