Immunotherapy has received widespread attention for its effective and long‐term tumor‐eliminating ability. However, for immunogenic “cold” tumors, such as prostate cancer (PCa), the low immunogenicity of the tumor itself is a serious obstacle to efficacy. Here, we report a strategy to enhance PCa immunogenicity by triggering cascade self‐enhanced ferroptosis in tumor cells, turning the tumor from “cold” to “hot”. We developed a transformable self‐assembled peptide TEP‐FFG‐CRApY with alkaline phosphatase (ALP) responsiveness and GPX4 protein targeting. TEP‐FFG‐CRApY self‐assembles into nanoparticles under aqueous conditions and transforms into nanofibers in response to ALP during endosome/lysosome uptake into tumor cells, promoting lysosomal membrane permeabilization (LMP). On the one hand, the released TEP‐FFG‐CRAY nanofibers targeted GPX4 and selectively degraded the GPX4 protein under the light irradiation, inducing ferroptosis; on the other hand, the large amount of leaked Fe2+ further cascaded to amplify the ferroptosis through the Fenton reaction. TEP‐FFG‐CRApY‐induced immunogenic ferroptosis improved tumor cell immunogenicity by promoting the maturation of DC cells and increasing intra‐tumor T cell infiltration. More importantly, recovered T cells further enhanced ferroptosis by secreting large amounts of IFN‐γ. This work provides a novel strategy for the molecular design of synergistic molecularly targeted therapy for immunogenic “cold” tumors.This article is protected by copyright. All rights reserved