tumor cells and distant lesions. [3] However, the immune-mediated tumor destruction following local PTT is always limited, and in situ combination using immunostimulants can enhance the antitumor immune response through activating innate immunity. [4,5] In addition, the recognition and processing efficiency of the released tumor antigens by immune system is another key parameter for the successful immune activation after PTT. Some studies have proposed that nanoparticles may be used to capture the released tumor antigens and deliver them to antigen-presenting cells (APCs), thereby inducing potent antitumor immunity, [6][7][8] after radiotherapy, microwave ablation, or PTT. In addition, to maximize the antitumor efficacy, the remodeling of immunosuppressive microenvironment of the so-called cold tumors is critically important. Therefore, we envision that a multifunctional nanoparticle as in situ vaccine to coordinate antigen capture and reactivation of immune suppression should be promising vaccination strategy to enhance the immune-mediated tumor clearance after PTT.As the natural nanoparticles secreted from Gram-negative bacteria, outer membrane vesicles (OMVs) receive significant attentions as vaccine delivery platform. [9,10] Due to the abundant pathogen-associated molecular patterns (PAMPs), Tumor antigens released from tumor cells after local photothermal therapy (PTT) can activate the tumor-specific immune responses, which are critical for eliminating the residual lesions and distant metastases. However, the limited recognition efficiency of released tumor antigens by the immune system and the immunosuppressive microenvironment lead to ineffective antitumor immunity. Here, an in situ multifunctional vaccine based on bacterial outer membrane vesicles (OMVs, 1-MT@OMV-Mal) is developed by surface conjunction of maleimide groups (Mal) and interior loading with inhibitor of indoleamine 2, 3-dioxygenase (IDO), 1-methyl-tryptophan (1-MT). 1-MT@ OMV-Mal can bind to the released tumor antigens after PTT, and be efficiently recognized and taken up by dendritic cells. Furthermore, in situ injection of 1-MT@OMV-Mal simultaneously overcomes the immune inhibition of IDO on tumor-infiltrating effector T cells, leading to remarkable inhibition on both primary and distant tumors. Together, a promising in situ vaccine based on OMVs to facilitate immune-mediated tumor clearance after PTT through orchestrating antigen capture and immune modulation is presented.