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Introduction: Diabetes mellitus is one of the most common metabolic disorders, which is accompanied by debilitating complications in the long term. Considering the therapeutic significance of medicinal plants, this study was conducted to evaluate the effects of i.p. intraperitonead administration of Apium graveolens on the serum glucose, triglyceride, total cholesterol, and HDL- and LDL-cholesterol levels of diabetic rats. Materials and Methods: Twenty-eight, female Wistar rats were divided into 4 groups, i.e. the control, AG-treated control, the diabetic, and AG-treated diabetic groups. The treatment groups received 200 mg/kg i.p. of the aqueous extract of the plant on alternate days for 4 weeks. Serum glucose, triglyceride, total cholesterol, LDL- and HDL- cholesterol levels were determined before the study, and two and four weeks after the study. Results: Serum glucose levels in diabetic group increased 2 and 4 weeks after the experiment as compared to data obtained one week before the study (P<0.001) AG treatment of diabetic rats did not have any significant effect. In addition, triglyceride levels in the diabetic group increased 4 weeks after the experiment in comparison to related data of one week before the study (P<0.05) and there was a significant lower level of triglyceride in AG-treated diabetic rats (p<0.01). Furthermore, a similar significant reduction was obtained for the treated-diabetic group as compared to the diabetic group regarding serum cholesterol levels (p<0.05). On the other hand, HDL- and LDL- cholesterol levels were significantly higher (p<0.05) and lower (p<0.01) in the AG-treated diabetic group as compared to the untreated diabetic group respectively. Conclusion: Although intraperitoneal administration of the aqueous extract of Apium graveolens has no significant hypoglycemic effect, it could possibly lead to appropriate changes in blood lipid profiles.