A wire bonder which includes a spool from which wire is drawn out, a capillary bonding head adapted to hold the wire and to extend the wire downwardly from the spool, and a tensioning mechanism. The tensioning mechanism includes a nozzle for directing a jet of gas against the wire with the nozzle being disposed in opposition to two guide plates disposed along the flow path of the gas ejected from the nozzle. The guide plates are spaced apart from each other to provide a space through which wire is passed from the spool to the capillary bonding head.