AbstractPhototherapy is effective for triggering the immunogenic cell death (ICD) effect. However, its efficacy is limited by low ¹O₂ generation and photothermal conversion efficacy due to two irreconcilable obstacles, namely the aggregation‐caused‐quenching (ACQ) effect and photobleaching. In this work, a discretely integrated nanofabrication (DIN) platform (Pt‐ICG/PES) is developed by facile coordination coassembly of cisplatin (Pt), photosensitizer molecules (indocyanine green (ICG)), and polymeric spacer (p(MEO₂MA‐co‐OEGMA)‐b‐pSS (PES)). By controlling the ICG/PES feeding ratio, the aggregation of ICG can be easily tailored using PES as an isolator to balance the ACQ effect and photobleaching, thereby maximizing the phototherapy potency of Pt‐ICG/PES. With the optimized ratio of each component, Pt‐ICG/PES integrates the complementarity of photodynamic therapy, photothermal therapy, and chemotherapeutics to magnify the ICD effect, exerting a synergistic antitumor immunity‐promoting effect. Additionally, temperature‐sensitive PES enables photothermally guided drug delivery. In a tumor‐bearing mouse model, Pt‐ICG/PES elicits effective release of danger‐associated molecular patterns, dendritic cell maturation, cytotoxic T lymphocytes activation, cytokine secretion, M2 macrophage repolarization, and distal tumor suppression, confirming the excellent in situ tumor ICD effect as well as robust systematic antitumor immunity. Ultimately, a versatile DIN strategy is developed to optimize the phototherapeutic efficacy for improving antitumor effects and strengthening systemic antitumor immunity.