Ir nanocatalyst Ir@CN was prepared by pyrolysis of the IrCl3 complex with 1,10-phenanthroline in the activated carbon. The iridium nanocatalyst Ir@CN was highly selective for the transfer hydrogenation of aldehydes and ketones including benzaldehyde derivatives, and the hydrogenative alkylation of C=O bonds was suppressed effectively. The iridium nanocatalyst Ir@CN is a heterogeneous catalyst and can be reused several times for the transfer hydrogenation of aldehydes and ketones. Ir nanocatalyst Ir@CN was prepared and the Ir@CN was found to be highly selective for the transfer hydrogenation of ketones and aldehydes including benzaldehyde derivatives in water. The iridium nanocatalyst Ir@CN is a heterogeneous catalyst and can be reused several times.