Gamma irradiated trans-chalcone (C15H12O) single crystals are investigated at 120 K using electron paramagnetic resonance technique. Trans-chalcone single crystals are irradiated with Co-60-gamma rays, at room temperature. The EPR spectra of gamma irradiated trans-chalcone single crystals are studied for different orientations of crystals in a magnetic field. The spectra are found to be temperature independent. The structure of the radical produced by gamma-irradiation of a single crystal of trans-chalcone is discussed. The investigation of EPR spectra of gamma-irradiated single crystals of trans-chalcone shows the presence of two trans-chalcone anion radicals. The two trans-chalcone anion radicals are created by the scission of the carbon-oxygen double bond. The reduction of trans-chalcone is identified which is formed by the addition of an electron to oxygen of the formed C-O bond. The principal values of the hyperfine coupling tensors of the unpaired electron and the principal values of the g-tensors and direction cosines of the radiation damage centers are determined. The results are found to be in good agreement with the existing literature.