In this manuscript, Cobalt (Co)-doped to Zinc Oxide (ZnO) samples prepared as thin films. These samples were obtained by utilizing spray pyrolysis have different concentrations of Cobalt. For investigating the effect of Co concentration on the thin films samples' physical properties, Different experimental techniques are employed. Such as Scanning Electron Microscope (SEM), X-ray diffraction, and optical spectroscopy. The grain size has been obtained using Scherrer's equation. From the obtained results, one can notice that the grain size behavior is non-linearly with the Co-concentration level. Electron Spin Resonance (ESR) is involved to observe the resonance absorption of microwave radiation of these thin films. It measures the spins of an electron of a molecule or an atom in a magnetic field. The study is performed before and after irradiation doses of 1 KGy and 3 KGy.The ESR signal shows the ferromagnetic response at room temperature which is improved after irradiation with Gamma-ray. The optical band gap of pure ZnO film was found to be 3.25 eV and the minimum bandgap is 3.11 for 1wt%. The existence of Co in the obtained film was confirmed by Energy Dispersive X-Ray (EDX) data. From the obtained results, the percentage of Co is increasing from 1.9% to 5.4% when the wt% is raising. In addition, the effect of the ionizing radiation doses; 1KGy and 3 KGy, on the magnetic and structural properties are investigated. As a result, Magnetic measurements for all prepared samples show a Room Temperature Ferromagnetic (RTFM) behaviour. Finally, increasing Co concentration and Gammaray irradiation dose will have a notified change on the ESR signal.