In this work, the gamma mass attenuation coefficient is investigated experimentally and theoretically for soil and oil-soil samples have been collected from different locations of Kirkuk city of Iraq. The oil-soil samples have been collected from some oil stations in Kirkuk oil field. The experimental measurements have been performed to obtain mass attenuation coefficients, using gamma spectrometer contains shielded NaI (Tl) detector at the energies of 59.5, 356.5, 662, 1173 and 1332 keV. Theoretically, the simulation results of mass attenuation coefficient using XCOM and Geant4 codes have been compared with experimental results and good agreement has been observed especially for Monte Carlo simulations code Geant4.