Composite reinforcement (R-2) that is self-adhesive by curing to a diene rubber matrix, which can be used as reinforcing element for a tire, comprising: at least one reinforcing thread (20), for example a carbon steel cord; a first layer (21) of a thermoplastic polymer, the glass transition temperature of which is positive, for example 6,6 polyamide, covering said thread; and a second layer (22) comprising an unsaturated thermoplastic stirene elastomer, the glass transition temperature of which is negative, for example an SBS (stirene-butadiene-stirene) copolymer, covering the first layer (21). Process for manufacturing such a composite reinforcement and rubber article or semi-finished product, especially a tire, incorporating such a composite reinforcement.