Rhodium nanoparticles supported on phosphorus-doped carbon (Rh/PC) are successfully prepared by the ball-milling method with sodium hypophosphite as the phosphorus source. The catalyst exhibits superb conversion (93.6%) and high regioselectivity (branched aldehydes/linear aldehydes = 20.2:1) for the hydroformylation of styrene compared to the phosphorus-free (Rh/C) and metal-free (PC) catalysts.