Manganese　dioxide　(MnO2)　shows　significant　potential　for　selective　catalytic　reduction　with　NH3　(NH3-SCR).　However,　the　selectivity　and　water　vapor　tolerance　of　MnO2　are　generally　unsatisfactory.　This　study　tackles　these　issues　by　decorating　tungsten　single　atoms　(W　SAs)　onto　MnO2　nanorods.　The　resulting　W/MnO2　catalysts　exhibit　markedly　improved　performance,　especially　the　1.8　wt%　W/MnO2　catalyst,　which　exhibits　superior　reactivity　(over　90%　conversion　and　over　80%　N2　selectivity)　across　an　extended　operational　temperature　range　of　75–350　°C,　along　with　improved　water　tolerance.　Structural　characterizations　based　on　X-ray　diffraction　(XRD)　and　aberration-corrected　scanning　transmission　electron　microscopy　(AC-STEM)　reveal　that　the　initial　W/MnO2　catalyst　is　characterized　by　W　SAs　that　are　partially　embedded　within　the　MnO2　lattice　and　partially　dispersed　on　the　surface.　During　the　reaction,　the　catalyst　undergoes　structural　transformations,　characterized　by　the　further　incorporation　of　surface-dispersed　W　SAs　into　the　MnO2　lattice.　The　incorporation　of　W　SAs　enhances　both　the　surface　acidity　and　oxygen　vacancy　density　of　the　catalyst,　thereby　improving　its　catalytic　performance.　In　situ　diffuse　reflectance　infrared　Fourier　transform　spectroscopy　(DRIFTS)　studies　suggest　that　the　NH3-SCR　reaction　proceeds　via　both　the　Langmuir-Hinshelwood　(LH)　and　Eley-Rideal　(ER)　mechanisms.　This　work　provides　valuable　insights　into　the　structure-performance　relationships　of　W/MnO2　catalysts　in　NH3-SCR,　offering　important　implications　for　the　design　and　fabrication　of　efficient　SCR　catalysts.　©　2025　Elsevier　Inc.