Abstract: The process for preparing 1,2-propanediol from propene and hydrogen peroxide comprises the steps of a) reacting propene with hydrogen peroxide in the presence of a catalyst mixture comprising a phase transfer catalyst and a heteropolytungstate, wherein the reaction is carried out in a liquid mixture comprising an aqueous phase having a pH of at most 6 and an organic phase, b) separating the biphasic mixture from step a) into an aqueous phase and an organic phase comprising propene oxide, c) recycling the propene oxide present in the separated organic phase into the reaction of step a) and d) separating 1,2-propanediol from the aqueous phase separated in step b).