Uranium-zirconium (U-Zr) alloy fuels have been taken into consideration for fast reactors because of their superior reactor safety, high uranium (U) density, and excellent thermal conductivity. In this paper, the structural and mechanical properties of metallic U and U-Zr alloy fuels are calculated at the atomic level by density functional theory–based calculations with Hubbard U (density functional theory + U) corrections. Several structure-property relations, such as lattice volume, bulk modulus, Young’s modulus, shear modulus, electronic density of states, etc. are calculated for U metal and U-Zr alloy fuels. In addition, the Zr content in metallic U fuel is adjusted from roughly 5 at. % to 15 at. % in order to determine how the Zr content affects the characteristics of U-Zr fuel material. A linear relationship between the volume and Zr concentrations is observed. The concentration of Zr in the fuel affects the mechanical characteristics of U-Zr alloy fuel. It is also observed that the electronic structure of the α-U phase is not changed significantly in the presence of Zr. Our computations provide insight into how U-Zr alloy fuels behave in reactor conditions.