Background: Acute sialadenitis is one of the major physical complications of radioactive iodine therapy (RAIT) for differentiated thyroid cancer (DTC). It is considered necessary to pay attention to the psychological impact on the patient as well as the physical influence during RAIT. Objective: To find evidence of the benefits of Basil tea on the psychological and physical side effects of RAIT. Methods: Forty-four DTC patients after total thyroidectomy were randomly divided into Group A (Basil tea group, n = 22) and Group B (Control group, n = 22). Subjects in Group A drank 180 mL of Basil tea prepared from 2.0 g of Holy basil (Ocimum tenuiflorum Linn.) leaves after each meal for four days, starting on the day RAIT was performed. Those in Group B drank the same amount of distilled water after each meal for the same period as those in Group A. The State-Trait Anxiety Inventory (STAI) was used to assess anxiety, while the saliva component test, and salivary gland scintigraphy were used to assess the oral cavity. Results: The rate of change of the STAI score (both State Anxiety and Trait Anxiety) was significantly lower in Group A than in Group B (P