The　expanding　demand　market　for　nanomaterials　has　led　to　the　substantial　release　of　metal　nanoparticles　(MPs)　into　the　environment　at　multiple　stages　of　their　life　cycle,　posing　risks　to　ecosystems　and　human　health　due　to　their　unique　physicochemical　properties.　MPs　entering　wastewater　treatment　plants　(WWTPs)　can　affect　the　nitrogen　removal　performance　of　wastewater　treatment,　especially　nitrous　oxide　(N2O)　emission　that　has　strong　greenhouse　effect　potential.　However,　a　systematic　understanding　of　the　effects　of　MPs　on　N2O　emissions　during　wastewater　treatment　is　lacking.　The　paper　reviews　the　fate　of　MPs　(ZnO,　Cu,　CuO,　Ag,　CeO2,　TiO2　nanoparticles)　in　WWTPs,　mainly　focusing　on　their　diverse　effects　on　N2O　emission　and　underlying　mechanism.　MPs　affecting　N2O　emissions　is　mainly　achieved　by　modulating　heterotrophic　denitrification　pathway,　because　of　the　higher　sensitivity　of　denitrifiers　to　MPs.　MPs　or　metal　ions　enter　the　cell,　disrupt　integrity　and　increase　permeability　of　the　membrane.　Their　introduction　not　only　suppresses　enzyme　activities　and　gene　expression　involved　in　N2O　production　and　consumption,　but　also　impedes　the　electron　transfer　process.　Furthermore,　these　nanoparticles　induce　changes　in　microbial　communities　engaged　in　nitrification　and　denitrification,　particularly　in　the　abundance　of　N2O-producing　and　reducing　microorganisms　in　denitrification.　And　existing　and　underlying　strategies　to　mitigate　the　effects　of　increased　N2O　emissions　from　MPs　in　wastewater　treatment.　This　work　presents　a　comprehensive　and　systematic　overview　of　the　fate　and　behavior　of　MPs　entering　WWTPs,　especially　the　performance　of　N2O　emissions,　providing　significant　implication　for　managing　the　associated　ecological　risks　and　achieving　carbon　neutrality.　©　2025　Elsevier　Ltd