Boehmite nanoparticles (AlOOH NPs) was found to be a highly active and green catalyst for the synthesis of highly substituted imidazoles under solvent-free conditions. This one-pot procedure is very simple, and affords good to excellent yields. Furthermore, the catalyst shows good thermal stability and recyclability. The catalyst was recycled for five runs without an appreciable loss in its catalytic activity. (C) 2013 Elsevier B.V. All rights reserved.