Local delivery of immune-activating agents has shown promise in overcoming an immunosuppressive tumor microenvironment (TME) and stimulating antitumor immune responses in tumors. However, systemic therapy is ultimately needed to treat tumors that are not readily locatable or accessible. To enable systemic delivery of immune-activating agents, we employ poly(lactic--glycolide) (PLGA) nanoparticles (NPs) with a track record in systemic application. The surface of PLGA NPs is decorated with adenosine triphosphate (ATP), a damage-associated molecular pattern to recruit antigen-presenting cells (APCs). The ATP-conjugated PLGA NPs (NP-ATP) are loaded with paclitaxel (PTX), a chemotherapeutic agent inducing immunogenic cell death to generate tumor antigens . We show that the NP-ATP retains ATP activity in hostile TME and provides a stable "find-me" signal to recruit APCs. Therefore, the PTX-loaded NP-ATP helps populate antitumor immune cells in TME and attenuate the growth of CT26 and B16F10 tumors better than a mixture of PTX-loaded NP and ATP. Combined with anti-PD-1 antibody, PTX-loaded NP-ATP achieves complete regression of CT26 tumors followed by antitumor immune memory. This study demonstrates the feasibility of systemic immunotherapy using a PLGA NP formulation that delivers ICD-inducing chemotherapy and an immunostimulatory signal.