Personalized cancer vaccination using nanomaterials holds great potential for cancer immunotherapy. Here, a nanochaperone (PBA‐nChap) is tailored for in situ capture of tumor‐associated antigens (TAAs) to improve cancer immunotherapy. The PBA‐nChap is capable of i) efficiently capturing TAAs in situ; ii) protecting TAAs from degradation; iii) transporting TAAs to antigen‐presenting cells and promoting cross‐presentation. Intratumor injection of PBA‐nChap in combination with pretreatment with photodynamic therapy (PDT) significantly enhances immune response and exhibits excellent antitumor efficacy. Moreover, nanovaccine prepared by simply co‐culturing PBA‐nChap with tumor cell fragments from surgery resected primary tumor in vitro synergized with immune checkpoint blockade (ICB) therapy can effectively inhibit tumor recurrence and metastasis after an operation. This work provides a promising platform for personalized cancer vaccination.