An adjustable shelf assembly for a refrigerator appliance includes a rear bracket and a rack positioned on the rear bracket. A pinion gear is meshed with the rack. A shelf frame is slidably mounted to the rear bracket. The pinion gear is rotatably mounted to the shelf frame. An actuator is positioned on the shelf frame. A line couples the actuator to the pinion gear such that the pinion gear is rotatable with the actuator via the line. The shelf frame is configured to move along a vertical direction relative to the rear bracket when the pinion gear is rotated by the actuator via the line. A related refrigerator appliance is also provided.