Chlorpyrifos (CPF) is a broad spectrum organophosphorus (OP) insecticide used in the control of a wide variety of insects. Its wide use in agriculture raises a growing public concern about the accumulation of these insecticides in food products and water supplies. The aim of this work was to evaluate the toxicological effect of CPF on thyroid and suprarenal glands. Twenty adult male albino rats were used in this work and divided into two groups: control (group І) and CPF-treated (group ІІ). The treated group received CPF daily in a dose of 5.4 mg/kg orally for 28 days. Serum T3, T4, TSH, corticosterone and malondialdehyde (MDA) were determined. The thyroid and suprarenal glands were evaluated for oxidative stress and microscopically. Results showed that CPF induced a significant decrease of serum T3 and T4 and a significant increase of serum TSH. Serum corticosterone was increased but statistically insignificant. Serum and tissues MDA were significantly increased. Histological examination of thyroid gland revealed that most follicles appeared degenerated with empty lumen due to decrease colloid, obvious exfoliation of the follicular epithelial cells and vascular congestion. Adrenals showed increased vacuolations of zona granulosa cells. Thus, it was concluded that chlorpyrifos exposure for 28 days causes damage to thyroid and suprarenal glands.