A refrigerator and a shelf assembly for a refrigerator are provided. The refrigerator may include a cabinet provided with a storage compartment, and a shelf assembly mounted in the storage compartment to adjust a height of a shelf. The shelf assembly may include a shelf mounted to vertically move in the storage compartment, a frame mounted to be vertically movable and support the shelf, at least one rotation gear provided at each of opposite sides of the frame, a pair of guide brackets provided at the opposite sides of the frame, a pair of sliders moved within the pair of guide brackets by the rotation gears, an exterior of each of the pair of sliders being provided with at least one protrusion, a power transmission to transmit rotatory power of the rotation gears to the pair of sliders, at least one guide groove formed on each of opposite inner surfaces of the storage compartment to guide movement of the protrusions, and a rotation device to rotate the rotation gears.