An optoelectronic sensor device for detecting precipitation on an outer surface (41) of a transparent pane (4) of a motor vehicle includes a beam guide element (1) having front and rear opposed parallel surfaces (2, 7) and first and second lateral opposed faces (5, 6). The front surface (2) is coupled to an inner surface (42) of a transparent pane (4) of a motor vehicle. Each of the lateral faces (5, 6) has a reflection region (52, 62). The rear surface (7) has first and second cut-out portions (8, 81) extending therefrom toward the front surface (2). Each of the cut-out portions (8, 81) has a reflective region (11). A beam transmitter (13) is disposed adjacent the rear surface (7) to transmit an infrared beam to the reflective region (11) of the first cut-out portion (8). The reflective region (11) of the first cut-out portion (8) reflects a beam transmitted from the beam transmitter (13) to the reflection region (52) of the first lateral face (5) which reflects the beam to the transparent pane (4). The transparent pane (4) reflects a part of the beam to the reflection region (62) of the second lateral face (6). The part of the beam reflected by the transparent pane (4) is a function of the precipitation on the outer surface (41) of the transparent pane (4). A beam receiver (14) is disposed adjacent the rear surface (7) to receive an infrared beam from the reflective region (62) of the second cut-out portion (81). The second lateral face (62) reflects the part of the beam reflected by the transparent pane (4) to the second cut-out portion (81) which reflects the part of the beam to the beam receiver (14).