Diabetes mellitus is one of the common and widely distributed metabolic diseases all over the world. This disease is characterized by hyperglycemia that results from defects in insulin secretion, insulin action or both. Different medicinal plant species are used as a traditional treatment for diabetes mellitus e.g. Ambrosia maritima, L. (Damsissa) which  is one of these plants that its extract was used to treat diabetic patients long times ago. Aim of the work: This work was aimed to investigate the antidiabetic, hypolipidemic and antioxidant effects of the aqueous extract of Ambrosia maritima, L. (Damsissa) on the alloxan-induced diabetic male albino rats. Material and Methods: This study was performed on thirty male albino rats with an average 100-110 g body weight. The animals were divided into three groups (10 /cage); Group I (Control untreated-group), Group II (Alloxan-induced diabetic group) and Group III (diabetic group treated orally with “28.5 mg/ kg body wt. twice/ day" of the plant extract). Results: The biochemical results showed marked decline (p<0.01) in the levels of the serum insulin, body weight, total proteins, albumin, globulin and HDL accompanied with marked elevation (p<0.001) in the levels of fasting blood glucose, levels of HOMA_IR, AST, ALT, GGT, urea, creatinine, uric acid, serum TC, TG, LDL, VLDL and ratios of TC/HDL and LDL/HDL (risk factors) in diabetic rats in comparison with the control group. Daily management of the diabetic rates with aqueous extract of Damsissa showed significant improvement in most of these parameters. Histologically, considerable improvement in the morphological changes that was observed in diabetic groups had been detected after treatment with Damsissa in liver, kidney and pancreatic tissues in comparison to the control group. Conclusion: It could be concluded that Ambrosia maritima, L. (Damsissa) can be used as an antidiabetic drug that can lower blood glucose concentration and guard against the negative effects of diabetes.