A knife with an extensible blade is formed by a handle that defines a cavity in which the blade is placed. The cavity is open at least on the side adjacent to the blade tip. In the cavity, at least one guiding groove is formed, which guiding groove is blind near the front edge of the handle. The blade is equipped with at least one guiding member corresponding with the guiding groove of the handle. The handle cavity is further equipped with a pull-out groove. A pulling element that selectively connects to the blade leads through and protrudes out of the pull-out groove when the blade is in a retracted position.