[en] Nanostructured CuO was successfully utilized for the synthesis of 1H-pyrazolo[1,2-b]phthalazine-5,10-dione derivatives via one-pot multicomponent reaction among phthalhydrazide, malononitrile and aromatic aldehydes under solvent-free conditions. Utilization of non-toxic and inexpensive catalyst, improved yields in short reaction times, wide substrate scope and easy purification of products are the important features of the developed protocol. The CuO nanocatalyst presents good reusability over five catalytic cycles.