An in-cabin monitoring system includes an electronic mirror provided inside a vehicle cabin, a camera that captures an image of an imaging target inside the vehicle cabin, and a light source that is provided in the electronic mirror and emits light into the vehicle cabin. The light source includes a plurality of light emitting diodes, and at least one light emitting diode of the plurality of light emitting diodes are disposed such that optical axes of the one or more light emitting diodes extend in directions different from a direction of an optical axis of an other light emitting diode of the plurality of light emitting diodes.