The invention provides a back support assembly mounted to the upright posts or canes of a wheelchair. The back support assembly can be adjusted independently with respect to a number of modes of adjustment including seat depth and width, the back height above the seat, and the angle of incline with respect to a plane defined by the wheel chair canes to which the back support is mounted. The back support assembly has a back support that is mounted at four points to cane clamps on each of the canes. A quick release mechanism is provided by a locking pawl on a mounting arm which permits single-handed release and removal of the back support from the mounting hardware while retaining the desired adjustment when the back support is remounted on the wheelchair. The back support assembly is frameless, and eliminates the additional weight that a support frame or carriage would add.