Two copper(I)–NHC complexes bearing an azide group were reacted with alkyne-decorated magnetic Fe3O4 nanoparticles without the use of an external copper source. In the case of the least sterically congested complex, the resulting nanoparticles displayed a catalytic activity in copper-catalyzed azide alkyne cycloaddition and some reusability highlighting the covalent grafting of the molecular catalyst by this mild and simple strategy.