In situ generation of Cu(0)-nanoparticles in the nanopores of modified montmorillonite and their catalytic activity in 1,3-dipolar cycloaddition reactions between azides and terminal alkynes to synthesise 1,2,3-triazoles have been carried out. The modification of montmorillonite was carried out by activation with H2SO4 under controlled conditions for generating nanopores to act as a “host” for the Cu(0)-nanoparticles, which is executed by successful loading of Cu(CH3COO)2 metal precursor through an incipient wetness impregnation technique followed by reduction with NaBH4. A TEM study reveals that Cu(0)-nanoparticles within the size range of 0–10 nm are evenly distributed on the support. The synthesized Cu(0)-nanoparticles exhibit face centered cubic (fcc) lattice geometry and serve as an efficient green catalyst for the “Click” azide–alkyne cycloaddition to afford highly regioselective 1,4-disubstituted 1,2,3-triazoles with excellent yields and selectivity in aqueous medium. The nanocatalysts can be recycled and reused several times without significant loss of their catalytic activity.