<p>Tungsten is a leading candidate material for plasma-facing applications in fusion devices due to its high melting point and sputtering resistance. However, neutron irradiation degrades its mechanical properties through defect accumulation and transmutation-product evolution. While high-fluence irradiation conditions with elevated Re and Os concentrations are known to promote embrittlement, the early-stage evolution of atomic environments and microstructures at lower fluence remains less understood. In this study, X-ray Absorption Spectroscopy (XAS) and high-energy X-ray Diffraction (XRD) were used to quantify the atomic and microstructural evolution of neutron-irradiated tungsten alloys, including single-crystal W, polycrystalline W, K-doped W, W-3Re, K-doped W-3Re, and La-doped W-3Re. Specimens were irradiated at 850 °C and 1100 °C to ~0.5 dpa. XAS revealed irradiation-temperature- and alloy-dependent local atomic environments. After irradiation at 850 °C, non-BCC environments associated with χ-phase (Re₃Os) and HCP-like structures were identified. At 1100 °C, additional χ-phase (Re₃Os and Re₃W) and Laves-phase Re₂W environments were quantified. XRD results showed alloy-dependent lattice evolution and defect retention, with Re-La-W and Re-K-W alloys exhibiting reduced lattice strain and lower defect concentrations relative to pure W specimens. Understanding these early-stage evolutions is crucial for developing strategies to mitigate late-stage precipitation effects through alloy design.</p>