Oleic acid was identified to catalyse bis(indolyl)methane and densely functionalized 4H-chromene, spirooxindole and spiro[indoline-3,4′-pyrano[2,3-c]pyrazole] derivative synthesis in good to excellent yields. The synergy between Brønsted acidity and surfactant ability of naturally available oleic acid was exploited to carry out the aforementioned transformations.