The invention relates to a process for the preparation of a thixotropic composition comprising polyurea particles, said process comprising contacting and reacting in a liquid medium reactants to form a polyurea and precipitating the polyurea to form polyurea particles, wherein acoustic vibration is applied during contacting of the reactants or as a post-treatment on the formed polyurea particles or both. The invention further relates to a thixotropic composition obtainable by the process, in particular thixotropic composition comprising high amounts of polyurea particles and optionally a polymer resin having high thixotropic efficiency. The compositions can be used, in particular as a masterbatch, in preparation of i.a. coating compositions.