The present study was designed to investigate the chemical composition of guava and mangoleaves, studying the phenolic compounds content, antioxidant activity of leaves extracts of guava and mango, and evaluation of guava and mango leaves on the plasma triglyceride and cholesterol of rats fed on hyperlipidemic diet. Also studying the effects of leaves extracts as antimicrobial agents. The results obtained through this work can be summarized in the following points: 1-    Chemical composition of guava and mango leaves The moisture content for guava and mangoleaves were (67.56 and 65.15%) respectively, protein (22.78 and 18.75%), total crude lipid (1.09 and 1.2%), crude fiber (15.5 and 20.9%), total ash (5.47 and 4.82%), and total carbohydrate (70.66 and 75.53%).Total phenolic compounds in leaves of guava and mangoextracts were 118.1 and 73.3 mg/g extract meanwhile total flavonoids were 11 and 9.75 mg/g extract respectively. 2-   Phenolic compounds of guava and mango leaves Phenolic compounds in methanol extracts of guava and mango leaves were analyzed by High Performance Liquid Chromatography (HPLC), guava and mango leaves contains 14 phenolic, analysis of guavaleaves extract showed that gallic acid, catechin, chlorogenic acid, naringenin and ellagic acid are the major phenolic compounds meanwhile catechin, pyro catechol, gallic acid and methyl gallate are the major phenolic compounds in mango leaves extract. 3-        In vitro antioxidant activity Reducing power assay, total antioxidant capacity and DPPH assay were used to evaluate the antioxidant activity of methanolic extracts of guava and mango leaves, for reducing power assay the reducing powers of methanol extracts of guava and mango leaves increased with an increase in their concentrations, and for DPPH assay, the antioxidant potential of guava and mango leaves extracts were further highlighted by the quenching of DPPH free radicals. The values of absorbance for leaves extracts ranged from 82.6 to 91.5% for guava and 58.8 to 74.7% for mango leaves extracts, for the total antioxidant capacity of the methanol extracts of guava, mango leaves and ascorbic acid, the values of absorbance were 0.103, 0.068 and 0.137 at concentration 100 µg/ml, and followed the order of effectiveness as:ascorbic acid > guava leaves extract > mango leaves extract. 4-        In vivo study of guava and mango leaves on hyperlipidemic rats a-     Treatment with guava and mango leaves decreased all lipid profiles significantly (triglyceride – total cholesterol – LDL-cholesterol – risk ratio and atherogenic index) and mixing of guava and mango leaves together gave more effect than guava or mango leaves individual. b-    Treatment with guava and mango leaves decreased significantly ALT and AST as compared with hyperlipidemic group and mixing of guava and mango leaves together gave more effect than guava or mango leaves individual c-     Treatment with guava and mango leaves were non-significant difference (P< 0.05) between hyperlipidemic group and group treated with guava and mango leaves for total protein, albumin, urea and creatinine. 5-    Histopathological changes of liver Positive control group (high fat diet) showing focal hepatic necrosis associated with inflammatory cells infiltration as well as congestion of hepatic sinusoids, while the administration of guava and mango leaves reversed the pathological changes and brought back the normal architecture of the liver. 6-    Antimicrobial activity Guava methanol extract recorded against Pseudomonas aeruginosa, Proteus mirabilis and Salmonella para typhi as Gram negative bacteria 16, 14 and 10 mm inhibition zone at concentration 3000 μg/disc, meanwhile recorded against Sacharomyces cerevisiae (yeast), Enterococcus and staphylococcus aureus as Gram positive bacteria 22, 18 and 15 mm respectively, for mango methanol extract the highest inhibition zone (11 mm) was recorded against Ralstonia at concentration 3000 μg/disc meanwhile Salmonella para typhi showed resistance to extract at all concentrations and Pseudomonas aeruginosa showed resistance to extract at concentrations 500 and 1000 μg/disc. The inhibition zone for Sacharomyces cerevisiae, Enterococcus and Staphylococcus aureus were recorded 14, 12 and 13 cm at concentration 3000 μg/disc respectively