The present invention relates to a device for entering a blood vessel using a winged needle with post-use protection, comprising a hollow protection body 20, which delimits an inner chamber 23 inside which a winged needle is slidably inserted. The needle body is slidingly movable along the inner chamber from a bare needle position, in which it is positioned in proximity of a front end 21 of the protection body with the distal portion 14 of the needle coming out through an exit opening 25 formed in it, to a needle-protected position. In a portion of the hollow protection body, in the vicinity of the exit opening, an additional opening 40 is formed, which additional opening extends in the longitudinal direction towards the exit opening 25. The additional opening is at least partially closed by a tongue 30, which extends projecting from the hollow protection body in the longitudinal direction towards the front end. The tongue is movable between a rest position, in which it closes at least partially the additional opening, and an operative position, in which it is divaricated from the hollow protection body so as to leave open the additional opening and widen the exit opening.
