Chicory (Cichorium intybus L.) leaves are used as food supplement and also in traditional medicine. The objective of this research was to determine the protective ability of chicory leaves extract against the toxicity induced by potassium dichromate in rats. Twenty four male rats were used in the present study and classified randomly into four groups (6 rats per group). The first group was served as a control and was given orally 1 ml of distilled water daily for four weeks, then injected intraperitoneally (i.p.) with 1 ml of saline solution 24 hours prior to decapitation. Group 2 was the K2Cr2O7−treated group; it received orally 1 ml of distilled water daily for four weeks, then i.p. injected with a single dose of K2Cr2O7 (30 mg/kg body weight, i.p.) 24 hours prior to decapitation. Group 3 was chicory treated group and was given orally chicory extract (250 mg/kg body weight, daily for four weeks), then injected with 1 ml saline solution (i.p.) 24 hours prior to decapitation. Group 4 received orally chicory extract (250 mg/kg body weight, daily for four weeks) prior to i.p. injection with a single dose of K2Cr2O7 (30 mg/kg body weight 24 hours before decapitation). Potassium dichromate induced a significant elevation in the levels of thyroid stimulating hormone (TSH), glucose, total cholesterol (TC), low−density lipoprotein cholesterol (LDL−C), total cholesterol/high-density lipoprotein cholesterol (TC/HDL−C) ratio, LDL−C/HDL−C ratio and trigylcerides (TG), as well as the activities of amylase and lipase enzymes in serum. Whereas, there is a significant decrease in free tri-iodothyronine (FT3), thyroxine (FT4), insulin and HDL−C levels in serum of K2Cr2O7−treatedrats. Treatment of rats with chicory extract alone decreased significantly the levels of serum FT4, TC, LDL−C, HDL−C, TC/HDL−C and LDL−C/HDL−C, while it increased significantly the amylase serum activity. The administration of chicory extract before the treatment with K2Cr2O7 could neutralize, to some extent, the harmful effects of K2Cr2O7 on the serum FT3, FT4, TSH, glucose, insulin, total cholesterol, LDL−C, HDL−C, TC/HDL−C, LDL−C/HDL−C and TG levels, as well as the activities of amylase and lipase enzymes. In conclusion, the results showed that the chicory extract may modulate changes in the biochemical parameters and thyroid hormones that were induced by K2Cr2O7 toxicity in rats.