Amino-functionalized mesoporous silica nanoparticles (MSN-NH) were synthesized by a post-grafting method and further studied as carriers for doxorubicin hydrochloride (DOX) delivery. The morphology, structure, and property of MSN-NH and DOX-loaded MSN-NH (DOX@MSN-NH) were studied using various techniques, such as transmission electron microscopy, Fourier transformed infrared spectroscopy, N adsorption-desorption isotherms, and zeta potentials. The drug loading and release profile as well as the in vitro cell cytotoxicity were detaily investigated. The results indicated that the loading content of DOX increased with the decrease of MSN-NH/DOX mass ratio and/or the increase of amino density. DOX@MSN-NH exhibited a pH-dependent drug release, drug release increased as the pH value decreased. Compared with MSN-NH, which were neglectable cytotoxicity against non-small-cell lung cancer (A549) cells, DOX@MSN-NH displayed remarkable cytotoxicity toward A549 cells in dose- and time-dependent manners. It was concluded that the as-synthesized MSN-NH could be used as promising drug carriers for cancer therapy.