Tin sulfide nanoparticles (SnS-NPs) were prepared in aqueous solution at room temperature on the surface of activated carbon (AC) and were investigated using field-emission scanning electron microscopy (FE-SEM), transmission electron microscopy (TEM), X-ray diffraction, reflective ultraviolet-visible spectrophotometry, and spectrofluorimetry. Calculations based on the SEM and TEM images showed that the sizes of the SnS-NPs immobilized on the AC were 30–70 nm. The prepared nanocomposite was used as a heterogeneous Lewis acid catalyst for the three-components one-pot synthesis of 4H-pyrano[2,3-c]pyrazole derivatives in ethanol at 80 °C. The reactions were efficiently performed in the presence of the prepared catalyst in short reaction times, and gave the desired products in high yields. This catalyst can be easily recovered by simple filtration and recycled up to eight consecutive times without significant loss of its efficiency.