A header for a combine harvester includes a conveyor belt for conveying crop material in a conveyance direction, and an adjusting device for adjusting a tension of the conveyor belt. The adjusting device includes a link that is movable with respect to a frame member of the header. The link is movable in a direction that is either orthogonal or substantially orthogonal to a tensioning direction of the conveyor belt for adjusting the tension of the conveyor belt. The conveyor belt may be an infeed conveyor belt or a lateral conveyor belt of a draper header, for example.