Photoimmunotherapy (PIT) is an emerging therapeutic approach that integrates phototherapy and immunotherapy to eliminate primary tumors under an appropriate dosage of local light irradiation, while simultaneously preventing tumor metastasis and recurrence by activating the host antitumor immune response. Tumor-responsive dynamic nanoassemblies (TDNs) have evolved from being a mere curiosity to a promising platform for high-performance PIT. However, the dynamic nano-bio interaction between TDNs and tumor microenvironment remains poorly understood, which shall be critical for precise control of TDNs assembling/disassembling behavior and superior PIT efficacy. To deepen the understanding of the structure–function relationship of TDNs, this review introduces the rational design, nano-bio interactions, and controllable functionalities of cutting-edge TDNs for enhanced PIT. Moreover, the synergetic mechanism between TDNs-based PIT and immunomodulatory agents-mediated immunomodulation is particularly emphasized. Finally, the challenges and future perspectives in this emerging field are assessed.