Aims: Stachys lavandulifoliaVahl is a frequently used plant to treat different diseases, but its probable toxic effects have not been reported yet. This study aimed to study the toxicity of the extract on rats' liver. Methods: In this experimental study, 100 rats were designated into 10 groups and injected normal saline or Stachys lavandulifolia Vahl extract at 50, 100, 150, and 200 mg/kg, intraperitoneally for 28 days. Four case groups and one control group were examined for ALT, AST and ALP after one month and the other groups were evaluated after two months. Results: In the fi rst month, the increase of ALP at all doses and the increase of AST at 200 mg/kg was significant, compared to the control group (p<0.05). In the second month, AST increased at the dosage of 150mg/ kg, and ALP decreased at the dosage of 100 mg/kg, compared to the control group (p<0.05). Histopathological assessment showed a signifi cant dose dependent increase both in necrotic-infl ammatory reactions and fi brotic lesions, in the fi rst and second months, compared to the control group (p<0.001). Conclusions: The Stachys lavandulifolia extract injected intraperitoneally has hepatotoxic effect, which is not eliminated by the drug withdrawal. Therefore, it is necessary to be consumed with caution (Tab. 4, Fig. 1