A method for revamping a urea plant of the type comprising a synthesis section (2) having a urea synthesis reactor (5), a thermal stripping unit (7) and at least one horizontal condensation unit (6), a treatment section (3) operating at medium pressure and a recovery section (4) operating at low pressure foresees the transformation of said at least one horizontal condensation unit (6) into a vertical condensation unit of the submerged type comprising a tube bundle and the provision of means (37, 41) for feeding a flow comprising ammonia and carbon dioxide in vapor phase and a flow of condensation liquid comprising carbamate simultaneously and independently in each of the tubes of said tube bundle with circulation inside said tubes in equicurrent from the bottom towards the top, and means (39, 50) for feeding at least one part of the feed carbon dioxide into said stripping unit (7) for use as stripping agent. Thanks to the present revamping method, the efficiency of the condensation unit (6) is substantially improved, consequently allowing an increase in its capacity and it is possible to leave out the medium pressure treatment section (3) thus obtaining a reduction in energy and maintenance costs.