The Schiff bases were prepared with aromatic aldehyde and aromatic amine using cashew shell extract as a catalyst under microwave irradiation. This reaction is rapid, efficient, and solvent-free and involves the one-pot synthesis of Schiff bases under microwave irradiation. The synthesized Schiff bases were characterized by Fourier transform infrared (FTIR) spectroscopy, 1H nuclear magnetic resonance (NMR) spectroscopy, 13C NMR spectroscopy, and gas chromatography–mass spectrometry (GC–MS). The advantages of the preparation of Schiff bases under microwave irradiation are high yield, shorter reaction time, easy, elimination of side products, and quick product isolation. The synthesized Schiff base derivatives are well known for their biological activity like antibacterial and antifungal activity.