In this study, the gamma radiation processing of tomato pomace samples was carried out at dose levels of 0, 1, 3 and 5 kGy. The total phenolic content, total flavonoids content and antioxidant activity properties of both non-irradiated and irradiated samples extracted in acetone 70%, methanol and chloroform: ethyl acetate (1:1) were assessed. The obtained data showed that, the total phenolic content increased with an increase in radiation dose for all extractions. Extracted Phenolic content from tomato pomace by using acetone (70%) was higher than those extracted by other solvents, whereas the phenolic content in acetone extract was increased from 182.579 mg GAE/100 g^-1 for the control sample to 191.445 mg GAE/100 g^-1 for the 3 kGy radiation-processed samples. Three methods were carried out to determine the antioxidant activity of tomato pomace, the first method was the radical scavenging activity against 2, 2′-diphenyl-1-picrylhydrazyl (DPPH), acetone extract exhibited greater scavenging activity than those extracted by other solvents. The same trend was also observed by using the second method of β- carotene bleaching assay and third method of ferric reducing antioxidant power (FRAP). The Highest ratio of β- carotene reducing power was achieved with acetone extract at 3 kGy whereas reached to 61.14%. Twelve phenolic acids component were identified in both non-irradiated and irradiated at 3kGy tomato pomace extracts by HPLC. Acetone extract of gamma irradiated and non-irradiated tomato pomace was tested for this antioxidant activity against oxidative stability of sunflower oil. The overall results indicated that, the highest oxidative stability (10.6 hr.) was obtained by using gamma irradiated tomato pomace at 3 kGy extract compared with those of the other doses. Finally, the obtained data showed that, tomato pomace is a very promising source of bioactive compounds and it is a very potential natural source of antioxidant compounds.