The invention relates to a bitumen/polymer composition containing at least one elastomer of the heat-crosslinkable S-B-S type, where S is a styrene or other vinylaromatic polymer block, and B is a polybutadiene block, the composition comprising an adjuvant of the olefin polymer type and having improved mechanical properties. The invention also relates to the use of the compositions in the fields of road applications such as hot mixes; warm mixes; cold mixes, for example cold-cast mixes or emulsion gravel; or surface dressings, for example fluxed bitumen or emulsions; and in the fields of industrial applications, for example in the production of inside and outside coatings.