A foldable luggage carrier includes a frame, a supporting tray and a pair of wheeled carriages. The tray has a pair of pivot brackets pivotally connected to two leg portions of the frame such that the tray is pivotable between a forwardly extended position and a fold-up position. Each of the pivot brackets includes a pair of opposed plates and a cam portion at a corner. Each of the wheeled carriages includes a wheel bracket having a sleeve bearing rotatably supported on the leg portions of the frame to permit the wheeled carriages to pivot between rearwardly extended positions and folded-in positions. The sleeve bearing has a guiding slope section at a bottom to interact with each cam portion of the pivot bracket in a manner such that the wheeled carriages automatically pivot to the folded-in positions and the rearwardly extended positions when the tray is moved between the fold-up position and the forwardly extended position.