Immune system evasion by cancer cells is one of the hallmarks of cancers, and it occurs with the support of tumor-associated immune cells (TICs) in the tumor microenvironment that increase the growth and invasiveness of tumor cells. With recent advancements in the development of novel near-infrared (NIR)-responsive nanoparticles, specifically eradicating TICs or inducing an inflammatory immune response by activating killer T cells has become possible. This review will discuss the mechanisms and applications of phototriggered immunotherapy in detail. In addition, various nanoparticles employed in phototriggered immunotherapy for cancer treatment will be covered. Furthermore, the challenges and future directions of phototriggered nanoparticle development for anticancer immunotherapy will be briefly discussed.