An automatically engageable and releasable brake apparatus adaptable to be attached to a wheelchair is provided, including a connection mechanism adapted to be positioned on a rear frame portion of the wheelchair frame, a seat actuation member adapted to be positioned on the wheelchair seat, a brake actuating member coupled to the connection mechanism and in fluid communication with the seat actuation member defining a closed fluid system therewith, and a brake member coupled to the brake actuating member and adapted to contact a ground surface on which the wheelchair is located. Occupational ingress into the wheelchair causes fluid to flow from the seat actuation member to the brake actuating member, which causes the brake member to move from a first position in substantial contact with the ground surface on which the wheelchair is located to a second position spaced a distance above the ground surface.