Designing a transformable nanosystem with improved tumor accumulation and penetration by tuning multiple physicochemical properties remains a challenge. Here, a near-infrared (NIR) light-driven nanosystem with size and charge dual-transformation for deep tumor penetration is developed. Methods: The core-shell nanotransformer is realized by integrating diselenide-bridged mesoporous organosilica nanoparticles as a reactive oxygen species (ROS)-responsive core with an indocyanine green (ICG)-hybrid N-isopropyl acrylamide layer as a thermosensitive shell. After loading doxorubicin (DOX), negatively charged nanomedicine prevents DOX leakage, rendering prolonged blood circulation time and high tumor accumulation. Results: Upon NIR light irradiation, mild photothermal effects facilitate the dissociation of the thermosensitive shell to achieve negative-to-positive charge reversal. Meanwhile, ICG-generated ROS cleave the diselenide bond of the organosilica core, resulting in rapid matrix degradation that produces DOX-containing smaller fragments. Such a light-driven dual-transformable nanomedicine simultaneously promotes deep tumor penetration and implements sufficient chemotherapy, along with evoking robust immunogenic cell death effects in vitro and in vivo. With the combination of a programmed cell death protein-1 (PD-1) checkpoint blockade, the nanotransformer remarkably blocks primary tumor growth and pulmonary metastasis of breast cancer with low systemic toxicity. Conclusions: This study develops a promising strategy to realize high tumor accumulation and deep penetration of light-transformable nanomedicine for efficient and safe chemo-immunotherapy.