The　ability　to　modulate　the　nonlinear　optical　(NLO)　response　of　low-dimensional　metal　oxides　is　highly　desirable　for　diverse　applications.　It　is　shown　here　that　the　irradiation　of　a　dispersion　of　2D　oxide　(MoO3)　nanosheets　(NSs)　by　femtosecond　laser　pulses　enables　simultaneous　scissoring　of　the　NSs　to　form　well-dispersed　MoO3　quantum　dots　(QDs)　and　the　modulation　of　the　NLO　response　in　the　visible　and　near-infrared　(NIR)　regions.　The　inversion　of　the　absorptive　nonlinearity　is observed combined　with　a larger　enhancement　of　NLO　response　in　the　laser-irradiated　MoO3−x　NSs　and　the　as-generated　QDs,　which　is　associated　with　the　steady　laser-deprival　of　oxygen　atoms　and　the　resultant　localized　surface　plasmon　resonance　due　to　electron　doping.　By　leveraging　the　sub-picosecond　NLO　response　of　the　plasmonic　MoO3−x　QDs,　the　development　of　ultrafast　optical　switches　is demonstrated for　ultrashort　pulse　laser　generation　based　on　fiber　lasers　operating　in　the　NIR　regions.　Furthermore,　the　strong　field　enhancement　of　these　non-noble　metal　plasmonic　QDs　is　exploited　for　the　fabrication　of　substrates　for　surface-enhanced　Raman　scattering,　which　demonstrate　a　detection　limit　down　to　the　part-per-billion　level.　This　work　delineates　an　efficient　strategy　for　creating　plasmonic　oxide　QDs　with　strong　NLO　response　that　is　attractive　for　photonic　applications.　©　2023　Wiley-VCH　GmbH.