A pre-tensioning device for pre-tensioning a backrest of a vehicle rear seat is provided. The backrest is situated in an upright seating position and configured to be pivotable about a pivot axis that extends in a vehicle transverse direction, in the direction of a folded position which in relation to the seating position is disposed to be repositioned toward the front. In order for a pre-tensioning device which can be produced in a more cost-effective and light-weight manner and can be attached in a more durable manner to be provided, the pre-tensioning device has at least one leaf spring which is configured to be supported at least indirectly on a vehicle body, and is supported at least indirectly on the rear side of the backrest that faces away from a passenger cabin.