A novel drug delivery system consisting of benzoic acid, 2-hydroxy-, 2-D-ribofuranosylhydrazide (BHR)-loaded solid lipid nanoparticles (BHR-SLNs) was prepared using the emulsification-evaporation technique. The mean particle size of the BHR-SLNs measured by photon correlation spectroscopy was about 75 nm. BHR-SLN morphology was assessed by transmission electron microscopy and atomic force microscopy. The drug entrapment efficiency was 70.2%, as determined via Sephadex gel chromatography and high-performance liquid chromatography. Drug release assessment in vitro showed that BHR was gradually released from SLNs in a time-dependent manner. Furthermore, treatment of 293T and Hela cells with BHR-SLNs demonstrated that BHR-SLNs were less toxic to normal cells while more effective in antitumor potency compared with the BHR drug alone. The results imply that BHR-SLNs could be considered as a promising antitumor drug system for a range of new therapeutic applications.