N-doped Li₂ZrCl_6−3xN_x chloride solid electrolytes were synthesized via a mechanochemical method, and the effects of N incorporation on crystal structure, Li local environment, and Li⁺ transport were systematically investigated. X-ray diffraction suggested that the main Li₂ZrCl₆-related diffraction features were largely retained, while N introduction induced partial structural evolution toward C2/m-related features. 7Li MAS NMR revealed that N incorporation sharpened Li resonance peaks. Among the series, Li₂ZrCl_5.7N_0.1 exhibited the highest room-temperature ionic conductivity of 1.15 mS cm⁻¹, with the lowest activation energy of 0.237 eV, demonstrating a reduced Li⁺ migration barrier. All-solid-state batteries incorporating Li₂ZrCl_5.7N_0.1 showed stable rate capability and long-term cycling, retaining 85.9% capacity after 500 cycles at 1C and 77.4% after 3000 cycles at 3C. These results suggest that appropriate N modification can tune the Li₂ZrCl₆-based structure and Li local environment, thereby improving Li⁺ transport in all-solid-state lithium batteries. This work provides a feasible strategy for improving chloride-based solid electrolytes for next-generation energy storage.