A mechanism for a reclining having a headrest and a backrest movable with respect to a seat, the backrest being supported by a reclining mechanism which includes an arc fastened to pads sliding in guiding plates, actuated by a motoreducer, and a mobile trapezoidal lever that is mobile backward and forward and that supports a bottom roller that is stationary and a top roller that is integral with the frame of the seat. The rollers are pivotable around axes that are parallel and are perpendicular to a longitudinal axis of the chair, so that, simultaneously with the shifting of the pads along the guiding plates, the frame of the seat performs a rheonomous tilting movement, upward or downward of its end corresponding to the anterior end of the chair seat.
