In this research, we synthesized and characterized a new heterogeneous basic nanocatalyst and its catalytic application was studied in the Claisen‐Schmidt and Knoevenagel condensations. In order to prepare this nanocatalyst, first, the Iranian natural asphalt was sulfonated with the concentrated sulfuric acid and then, converted to the potassium natural asphalt sulfonate (K‐NAS). In order to characterization of the nanocatalyst, used of FT‐IR spectroscopy, scanning electron microscopy (SEM), energy dispersive spectroscopy (EDS), X‐ray diffraction (XRD), inductively coupled plasma (ICP) and thermogravimetric analysis (TGA) techniques. This new basic heterogeneous nanocatalyst have advantages such as being eco‐friendly, huge specific surface area, high reactivity and recyclability.