We report for the first time an organic nanoparticle based nuclear-targeted photoresponsive drug delivery system (DDS) for regulated anticancer drug release. Acridin-9-methanol fluorescent organic nanoparticles used in this DDS performed three important roles: (i) ″nuclear-targeted nanocarrier″ for drug delivery, (ii) ″phototrigger″ for regulated drug release, and (iii) fluorescent chromophore for cell imaging. In vitro biological studies reveal acridin-9-methanol nanoparticles of ~60 nm size to be very efficient in delivering the anticancer drug chlorambucil into the target nucleus, killing the cancer cells upon irradiation. Such targeted organic nanoparticles with good biocompatibility, cellular uptake property, and efficient photoregulated drug release ability will be of great benefit in the field of targeted intracellular controlled drug release.