In the present work, the gamma-ray energy absorption buildup factor for water and dose buildup factor for soft tissue (ICRU ۴-component), A-۱۵۰ tissue-equivalent plastic (A۱۵۰TEP), and tissue equivalent-gas, methane-based (TEGMB) were studied for ۳۵۶, ۶۶۲, ۱۱۷۳, and ۱۳۳۲ keV gamma-ray energy up to depths of ۱۰ mean free path (mfp) extensively using Monte Carlo simulation. The aim in this paper is to investigate the gamma buildup factor for soft-tissue equivalent materials and more specifically to study the relative difference between them at practical gamma energies through the Monte Carlo simulation method. The simulations have been performed by MCNPX code, which could be very useful for calculation of shielding estimates. The results revealed that by using the MCNPX code one can easily calculate the energy absorption and dose buildup factors for different materials and also different energies. The simulation results for water were verified by comparing data with those of experimental works wherever possible. In addition, the simulation results for soft tissue were verified by the G-P fitting method, as well. Moreover, the simulation results of the total mass attenuation coefficients of water, A۱۵۰TEP, soft tissue, and TEGMB were compared with standard database of NIST-XCOM and a good agreement has been obtained. The materials selected have been studied for the first time in this work with respect to the gamma buildup factors at specific energies mentioned above by the Monte Carlo simulation method.