Tumor cells are dominant in the nutritional competition in the tumor microenvironment (TME), and their metabolic abnormalities often lead to microenvironmental acidosis and nutrient deprivation, thereby impairing the function of immune cells and diminishing the anti-tumor therapeutic effect. Herein, we report a branched polymeric conjugate and its efficacy in attenuating the metabolic competition of tumor cells. Compared with the control nanoparticles prepared from its linear counterpart, the branched conjugate-based nanoparticles (branched NPs) could more efficiently accumulate in the tumor tissue and interfere with the metabolic processes of tumor cells to increase the concentration of essential nutrients and reduce the level of immunosuppressive metabolites in the TME, thus creating a favorable environment for infiltrated immune cells. Its combined treatment with an immune checkpoint inhibitor (ICI) achieved an enhanced anti-tumor effect. Our work presents a promising approach for targeting the metabolic competition in the TME to enhance the chemo-immunotherapeutic effect against cancers.