A fragrance diffuser device for motor vehicle interiors, of the type including an elongated support body, a refill of a fragrance-impregnated plastic material fixed to a fastening base of the support body, and an elastic clamp to hook the diffuser onto a motor vehicle ventilation system grid. The fastening base consists of a rib longitudinally extending for at least part of the support body length and retaining by friction the refill of a fragrance-impregnated plastic material which at least partially surrounds the rib.