We report in this letter the observation of visible photoluminescence (PL) at room temperature from hydrogenated nanocrystalline silicon (nc-Si:H)/amorphous silicon (a-Si:H) multilayers (MLs) prepared in a plasma enhanced chemical vapor deposition system without any postprocessing. The PL peak wavelength can be controlled, blueshifting from 750 to 708 nm, through reducing the width of the nc-Si:H sublayers from 4.0 to 2.1 nm. Quantum size effect in nc-Si:H sublayers of the ML is responsible for the emission above the band gap of bulk crystal Si.