Abstract: A headrest device particularly adapted for removable installation upon the non-rigid backrest of a chair or wheelchair, comprising a first elongate member of generally U-shaped configuration, upon the upper part of its arms, a pillow-like head-contacting member is supported. A second elongate member resides in a plane generally parallel to and spaced from the plane of the first member, and means are provided on the upper ends of the arms of the second member for slidable attachment to the arms of the first member. The spaced-apart relation of the first and second members permits the backrest of a chair or wheelchair to be received therebetween. Finger operated locking means may be provided for securing the arms of the second member to the arms of the first member such that undesired movement of the head-contacting member away from a selected position on the backrest of the chair or wheelchair can be prevented.