By quenching the electronic excited state, self-aggregation of photosensitizers deteriorates the photodynamic therapy (PDT) outcome. Previously reported strategies to mitigate aggregation-caused-quenching (ACQ) involve harsh conditions and tedious synthesis processes. Moreover, failure to tune the extent of photosensitizer aggregation on-demand usually leads to a sub-optimal PDT effect. Herein, a new insight into ACQ alleviation by precisely tailoring the aggregation extent of photosensitizers via the confinement effect is unraveled by concise and facile coordination co-assembly fabrication of Pt/TCPP NCPs. Optimized meso-tetra(4-carboxyphenyl)porphine (TCPP) aggregation extent was achieved by precisely regulating the PES/TCPP feeding ratio to 12, unleashing outstanding PDT efficacy for robustly synergistic cancer PDT/chemotherapy.