L-Proline is known as the most favored organocatalystin enamine-mediated reactions. Magnetic functionalization of this organocatalyst could solve its recovery and reuse problems. Herein we report the use of magnetic L-proline nano-biocatalyst for a simple and efficient one-pot coupling reaction of dimedone,malononitrile, and aromatic aldehydes to afford the corresponding tetrahydrobenzo[b]pyrans as a significant class of heterocyclic compounds with great biological and pharmacological importance according to a green protocol. Low cost, facile handling, simple preparation, highstability, reusability,and low toxicityare some remarkable features ofthis nano-biocatalyst.