The present study aimed at investigating the possible protective effect of green tea on thyroid damage. This was accomplished by the model of amiodarone induced thyroid damage in albino rat. The possible thyroid changes secondary to green tea overconsumption were also determined. Twenty four adult male albino rats were divided into 5 groups: Group 1 (Control Group) of 4 rats. Group 2 (Green Tea Group) of 5 rats, each given 50mg/kg of green tea extract tablets dissolved in 0.5 ml distilled water orally. Group 3 (Overconsumption Group) of 5 rats, each given 1000mg/kg of green tea extract dissolved in 2.5ml distilled water orally. Group 4 (Amiodarone Group) of 5 rats, each given 30mg/kg daily orally. Group 5 (Amiodarone and Green Tea Group) of 5 rats, each given amiodarone 30mg/kg and green tea extract 50mg/kg daily orally. Thyroid function tests were performed. Rats were sacrificed after 6 weeks. Thyroid sections were subjected to histological, histochemical, immunohistochemical and morphometric studies. A serological study and statistical analysis were also performed. Group 3 demonstrated some follicles with cellular masses extending into the lumen, some other distorted follicles, few follicles with dislodged nuclei or cellular debris into the lumen, few follicles containing crescents of colloid and some follicles devoid of colloid. Group 4 recruited multiple follicles with crescents of colloid and multiple follicles exhibiting colloid with large peripheral vacuolations. Some follicles were focally lined by more than one layer of nuclei and occasional follicles were lined by more than one layer of nuclei. Vacuolated cytoplasm and dark nuclei were observed in multiple lining follicular cells in both group 3 and 4. In group 5 multiple lobules contained few follicles with large peripheral vacuolations of colloid. Few lobules demonstrated some follicles containing crescents of colloid. Increased interlobular and interfollicular collagen fibers were found in groups 3 and 4. PAS reaction was confirmative in groups 3 and 4. In addition, group 4 revealed discontinuous strong PAS+ve reaction at foci of disrupted basement membrane. In group 3, few PCNA +ve nuclei of follicular cells, some +ve nuclei in masses extending into the lumen and few +ve dislodged nuclei were found. In group 4, multiple PCNA +ve nuclei were seen in follicular cells and in follicles partially lined by more than one layer of follicular cells. In group 5, some PCNA +ve nuclei were found in follicular cells. A significant increase in the mean area of connective tissue fibers and that of PCNA +ve nuclei were recorded in groups 3 and 4. The mean area of colloid indicated a significant decrease in both. A significant decrease in the mean value of TSH was found in groups 3, 4 and 5.In conclusion, green tea proved to have an ameliorating effect on the amiodarone induced cytotoxic and proliferative changes of thyrocytes. In addition, regression of fibrotic changes in the gland was recorded. On the other hand, overconsumption of green tea resulted in proliferative and cytotoxic effects on thyrocytes, even more marked in comparison to amiodarone cytotoxic effect.