Despite the outstanding clinical success of immunotherapy, its therapeutic efficacy in glioblastoma (GBM) is still limited. To identify critical regulators of GBM immunity, we constructed a mouse single-guide RNA (sgRNA) library corresponding to all disease-related immune genes, and performed an in vivo CRISPR knockout (KO) screen in syngeneic GBM mouse models. We demonstrated that the deletion of GDF15 in GBM cells ameliorated the immunosuppressive tumor microenvironment (TME) and enhanced the antitumor efficacy of immune checkpoint blockade (ICB) response. Moreover, we designed unique nanoparticles for efficient encapsulation of CRISPR-Cas9, noninvasive brain delivery and tumor cell targeting, demonstrating an effective and safe strategy for GDF15 gene therapy. The CRISPR-Cas9 nanoparticles, known as ANP