There is disclosed a portable electronic instrument, such as a wristwatch (1), including a case (2) enclosing an electronic module (6) and a display device (5), a crystal (3) fitted onto the case (2), an electric power supply source (4) housed in the case (2) and powering the electronic module (6) and the display device (5), and an antenna (20) for receiving and/or transmitting radio-frequency signals electrically connected to the electronic module (6). The case (2) includes an exterior body (4) including a bottom (4a) and lateral walls (4b) and a bezel element (7) fitted onto the exterior body (4) and supporting the crystal (3). The antenna (20) rests on an outer face (7a) of the bezel element (7).