Background: Dosimetry is a fundamental part of the radiation processing industry. Aqueous inorganic dosimeters have been used for gamma radiation dosimetry such as standard ferrous sulfate dosimeter. The purpose of this study was to investigate the effect of gamma radiation on the diethyl fumarate DEF in dimethyl sulfoxide DMSO solution and its possible use in chemical dosimetry. Materials and Methods: Three solutions having different concentrations of DEF were prepared (5, 10 and 20%) and exposed to various gamma doses. Irradiation was carried out using ROBO facility of ⁶⁰Co gamma ray. Absorbance was measured using Melton Roy 1201 UV-VIS spectrophotometer. Results: The absorption spectra of irradiated solution showed broad absorption bands between (325-400nm) with a shoulder at 332 nm. The absorbance increased with increasing the dose. Good response and linear relationship were found between absorbed dose and absorbance of 10% and 20% DEF concentration in the range of 0-225 kGy at the measured wavelength. Good dose rate independence was observed in the range of 14-33 kGy/h. It was noticed that irradiated samples had a good stability in darkness. Whereas, the response was affected during the storage in day light. This response was found to be depended on the irradiation temperature within the range of 18- 52 ⁰C. Conclusion: Our measurements showed that the ability of using the solution of diethyl fumarate DEF in dimethyl sulfoxide DMSO as a high dose radiation dosimetry. The useful dose range for 10% and 20% DEF of concentrations is up to 225 kGy. Nevertheless, the correction of temperature for routine dosimetry measurements should be taken into account.