Aluminium (Al) is an environmental xenobiotic that induces disruption in pituitary-thyroid function. Zinc is essential for many biochemical processes and for cell proliferation. The aim of this study was to analyze the thyroid toxicity induced by Al in rats and to evaluate the possible ameliorative effect of zinc. The study was conducted on forty male albino rats randomly divided into 4 groups: control group, zinc group treated with zinc sulphate (2 mg/kg), Al group treated with AlCl3 (20 mg/kg), and AlCl3 (20 mg/kg) + Zn (2 mg/kg) group. Rats were treated orally once daily for 30 consecutive days. At the end of the experiment, rats given aluminium alone had significantly higher MDA (malondialdehyde), superoxide dismutase in thyroid tissue and lower serum T3, T4 and TSH levels than the control group. Co-treatment of zinc with aluminium had an ameliorative effect on the previous parameters. Light and electronic microscopic investigations revealed that aluminium caused marked degenerative changes in the thyroid of rats. Restoration of the normal architecture of thyroid tissues were observed in rats received aluminium + zinc combination. Thus, aluminium can induce oxidative damage in rat thyroid and zinc has an ameliorative effect against this damage.