Abstract Water-soluble triaryl phosphine oxides bearing polyether moiety proved to be efficient ligand for rhodium catalyzed aqueous/organic two-phase hydroformylation of water-immiscible oleyl alcohol. Under the selected conditions, yield of aldehydes reached 83.3% with 70 h −1 of TOF. The in situ formed catalyst was easily separated from the reaction mixture and could be employed in the successive reaction runs. It was observed that the catalyst exhibited high activity in the isomerization of oleyl alcohol during the hydroformylation. As a result, 19% of hydroformylation product was determined to be 18-formyl-octaldecyl-1-ol.