This research investigates the effects of molybdenum trioxide (MoOs) on the gamma radiation shielding efficiency of phosphate glasses. The study focuses on a sequence of glass samples with varying compositions: xMoO3-(30-0.5x)-(30-0.5x)Na2O-(30-0.5x)-(30-0.5x)ZnO-40P2O5, where parameter x was adjusted from 10 (S1) to 60 (S6) in 10 mol% increments. The glass samples exhibited different densities, with values ranging from 3.01 g/cm3 to 3.15 g/cm3. The mass attenuation coefficients (MAC, cm2/g) of all the glasses were determined across 0.015-15 MeV energy range using the EpiXS software. To ensure the reliability of the results, the mass attenuation coefficients of the S1-S6 glasses were further evaluated using the MCNPX Monte Carlo simulation code at specific energies: 0.662 MeV, 1.173 MeV, and 1.333 MeV, corresponding to commonly used radioisotopes such as 60Co and 137Cs. The comparison between the EpiXS and MCNPX results revealed a robust correlation, supporting the accuracy of the data obtained. Furthermore, the obtained MAC results were utilized to estimate various related parameters, such as linear attenuation coefficient, half- and tenth-value layers, mean free path, as well as effective atomic numbers and electron densities. The findings demonstrate that the investigated phosphate glasses, especially those with a high MoO3 content, present a significant potential for applications requiring efficient radiation shielding.