In an apparatus on a spinning preparation machine, for example, a flat card, draw frame or the like, for monitoring at least one sliver, having two rotating rollers that form a roller nip through which at least one sliver passes, an optical monitoring arrangement (sensor) that monitors the presence of the sliver is provided in the vicinity of the rollers. To permit a reliable and trouble-free monitoring of sliver breakage in a structurally simple manner, the sensor arrangement is arranged in the region between the shared tangents to the peripheral surfaces of the rollers, the tangents being arranged perpendicularly to the running direction of the fiber, and the optical path of the sensor runs parallel to the axles of the rollers.