Vehicular driver monitoring system with DMS camera at interior rearview mirror assembly

A vehicular driver monitoring system includes an interior rearview mirror assembly having a mirror head adjustably attached at a mounting base configured to attach at an interior portion of a vehicle. A driver monitoring camera is accommodated by the mirror head so as to move in tandem with the mirror head when the mirror head is adjusted relative to the mounting base to adjust a driver's rearward view. At least one near infrared light emitter is accommodated by the mirror head and is operable to emit near infrared light toward a head region of the driver of the vehicle. Image data captured by the driver monitoring camera is processed to determine driver attentiveness and/or driver drowsiness. The vehicular driver monitoring system adjusts processing of the captured image data to accommodate adjustment of the mirror head when the driver adjusts the mirror head to adjust his or her rearward view.