Tribulus terrestris (Tt) is a herb distributed worldwide due to its beneficial claims on many diseases. This study aimed to study the role of Tt against Cadmium (Cd)-induced toxicity on thyroid gland of adult male albino rats. Twenty-four rats were subdivided into four groups; (Control group) without any treatment, (Tt + Cd group) with a daily oral dose of Tt (5 mg/ kg b. wt.) for eight weeks, from the beginning of the ninth week, they injected i.p. with 2 mg/kg of CdCl4 for 8 days, (Cd group) injected i.p. with 2 mg/kg of CdCl4 for 8 days, (Cd + Tt group) injected i.p. with 2 mg/kg of CdCl4 for eight days, from the ninth day they were given a daily oral dose of Tt (5 mg/ kg b. wt.) for eight weeks. Results revealed that levels of T4 and TAC decreased while levels of TSH and MDA increased in Cd group resulted in follicular cells degeneration, increasing the amount of collagen fibers, and increased positive immunoreactivity of PCNA. Administration of Tt before Cd injection increased levels of T4 and TAC while decreased levels of TSH and MDA. administration of Tt after Cd injection didn't affect T4, TSH, MDA and TAC levels. The pre-treatment with Tt protects the thyroid tissue from those destructive changes by Cd while the post-treatment did not treat them.  In conclusion, Tribulus terrestris is highly effective in shielding the thyroid gland from further damaging effects of Cd -induced oxidative stress when utilized as prophylactic antioxidant rather than treatment therapy.