Background: The use of ¹³¹I in thyroid diseases is responsible for oxidative stress due to increased production of reactive oxygen species that may lead to multiple disorders in human. Purpose of this study was to mitigate the oxidative stress, generated by ¹³¹I therapy, by supplementation of phytoprotectants. Materials and Methods: After eliminating absconders, 97 volunteers of benign and malignant hyperthyroid diseases viz. control (n=42), standard (n=23), turmeric (n=19) and green cardamom (n=13) groups participated in this study. Vitamins were administered orally in standard group while turmeric (Curcuma longa) and green cardamom (Eletteria cardamomum) as phytoprotectants were given orally in the respective groups, 5 days before ¹³¹I therapy. The malondialdehyde (MDA) was measured in serum before (baseline), at 3-hours and after 2-weeks of ¹³¹I administration. Results: After radioactive iodine therapy (RAIT), there was a continuous decline of serum MDA in vitamin group (3.57 to 2.64 µmol/L) in contrast to the control, where there was a ceaseless rise (3.01 to 3.69 µmol/L) in the oxidative stress in terms of MDA. In akin to the standard group of vitamins, there was incessant decrease in both the treatment groups of green cardamom (3.55 to 2.89 µmol/L) and turmeric (3.45 to 2.06 µmol/L). The turmeric was proved as better phytoprotectant. Conclusion: The turmeric and green cardamom are good scavengers of free radicals and can be used as supplements along with ¹³¹I, in thyroid patients as radioprotective agents. The turmeric is more potent radioprotectant as compared to green cardamom.