||Sonodynamic therapy (SDT) is an emerging cancer treatment that utilizes cytotoxic reactive oxygen species (ROS) for eradicating tumors and elicits antitumor immunity via immunogenic cell death. Despite these prominent intrinsic, in vivo applications of SDT has been restricted, owing to poor bioavailability of sonosensitizers. Here, we develop biocompatible sonosensitizer nanoparticles (SNPs) that can generate ROS in the presence of US. SNPs were composed of carboxymethyl dextran and chlorin e6 to prepare self-assembled polymeric nanoparticles, and polyethylene glycol was additionally attached to improve in vivo stability. In cell experiments, SNPs showed considerable cytotoxic effect through SDT, and SDT-treated cells induced maturation of bone-marrow-derived dendritic cells by releasing pro-inflammatory molecules and tumor-associated antigens. Further, SNPs-mediated SDT showed in vivo therapeutic efficacy on metastatic tumors when it applied with anti-PD-L1 immune checkpoint blockade.