A foldable walker includes a front frame having left and right pin holes, two side frame units pivotably connected to the front frame, and two locking units. Each locking unit is disposed between the front frame and the respective side frame unit, and includes a lock releasing lever and a locking pin. The lock releasing lever has a pulling fulcrum portion, an operating portion opposite to the pulling fulcrum portion, and a pressing fulcrum portion disposed therebetween. An upwardly pulling action or a downwardly pressing action onto the operating portion permits rotation of the respective side frame unit between folded and unfolded positions. The locking pin is disposed between the pulling and pressing fulcrum portions to be inserted into the respective pin hole to lock the side frame units to the unfolded position, and is moved by the upwardly pulling action or the downwardly pressing action.