Nano-WO3-supported sulfonic acid [n-WO3-SO3H (n-WSA)] is easily prepared from the reaction of nano WO3 with chlorosulfonic acid as sulfonating agent. This new catalyst is characterized by X-ray diffraction (XRD), field emission scanning electron microscopy (FE-SEM), FT-IR spectroscopy, thermal gravimetric analysis (TGA), pH analysis and Hammett acidity function. Nano-WO3-supported sulfonic acid is used as an efficient and recyclable catalyst for some organic reactions such as synthesis of 1,8-dioxo-octahydroxanthene, tetrahydrobenzoxanthene and benzimidazolo quinazolinone derivatives. All of the reactions are very fast and the yields are excellent. The used catalyst was easily separated and reused for 10 runs without appreciable loss of its catalytic activity. (C) 2014 Elsevier B.V. All rights reserved.