In this study, experimental and theoretical work on barite concrete with nanomaterials against gamma and neutron radiations were implemented. Besides density, radiation energy, and the type of aggregate, which are the main variables in radiation attenuation, the researchers focused on nanomaterials with a higher atomic number such as TiO2 and Fe2O3, and those with favorable filling and hydration effect such as SiO2 along with their hybridization as an addition to the barite concrete. Nanomaterials were added with 0, 1, 3, 6, and 9% of cement weight to experimentally investigate the mechanical properties, microstructure, and gamma radiation characteristics. The same mixes of elements and quantities were used in the theoretical work in addition to 12 and 15% nanomaterials and along with the material’s data of a gravel concrete from a previous work to optimize the mixes that are capable of shielding both gamma and neutrons radiations. The correlated results indicated higher experimental gamma attenuation coefficients than the theoretical ones and the good effect exhibited by the addition of the nanomaterials; especially TiO2 and Fe2O3, which added to the mechanical strength and gamma shielding of the barite concrete. The optimization process gave the required densities, moderators’ fractions, and barite-gravel content in the mix that are required to shield against both gamma and neutron radiations and proved essential in designing mixes with adequate shielding mechanism.