Disclosed is a mechanical holder for a mobile device on board a vehicle, including two jaws that are rotatably hinged about an axis and close on the mobile device, the closing movement of the two jaws being such that, regardless of the mobile device engageable with the mechanical holder, the position of the mobile device is identical. The two jaws each have a gear wheel secured thereto, wherein the gear wheel is mounted on an axis parallel to the axis of rotation of the jaws and engages with the other wheel to form a gearing and to allow each jaw to rotate simultaneously and identically relative to the axes of rotation of the respective gear wheels thereof.