Ultrasound (US), a nonconventional energy source, has become a very popular and useful technology in organic chemistry. Several examples of US-assisted reaction have indicated that high yields and short reaction times are reasonable, and applications of this energy transfer process on click reactions have been published. Stable, water-soluble copper nanoparticles (Cu NPs) were synthesized using a double-hydrophilic block copolymer as a template. The prepared Cu NPs were effective as catalysts for the [3+2] cycloaddition of azides with terminal alkynes to provide products in good yields and with high regioselectivity. An environment-friendly process of synthesizing regioselective triazoles was developed from a variety of azides with terminal alkynes, in which the water-soluble Cu NPs were utilized, under 10 min sonication. The Cu NPs can be reused three times under the present reaction conditions, without any loss of catalytic activity. Block copolymer nanoreactors were shown to be promising in creating a number of water-soluble catalytic metal NPs for a wide variety of organic transformations.