Photodynamic therapy (PDT) is a cancer treatment that uses photosensitizing compounds (photosensitizers) to generate reactive oxygen species (ROS) upon activation by light. This process induces a strong local inflammatory response and activates the adaptive immune system, leading to tumor destruction and immune memory. The review discusses the latest scientific reports on the adaptive immune response induced by ROS in PDT, including the mechanisms of ROS generation, the activation of the innate and adaptive immune responses, and the challenges posed by the tumor microenvironment (TME). Recent studies have explored the combination of PDT with other therapies, such as checkpoint-blocking immunotherapy, chemotherapy, and radiotherapy, to enhance immunogenic cell death and improve cancer therapy. The review also highlights the potential of PDT in inducing immune memory and preventing cancer recurrence. Despite the promising results, further research is needed to optimize PDT protocols and address the limitations of the TME.Photodynamic therapy (PDT) is a cancer treatment that uses photosensitizing compounds (photosensitizers) to generate reactive oxygen species (ROS) upon activation by light. This process induces a strong local inflammatory response and activates the adaptive immune system, leading to tumor destruction and immune memory. The review discusses the latest scientific reports on the adaptive immune response induced by ROS in PDT, including the mechanisms of ROS generation, the activation of the innate and adaptive immune responses, and the challenges posed by the tumor microenvironment (TME). Recent studies have explored the combination of PDT with other therapies, such as checkpoint-blocking immunotherapy, chemotherapy, and radiotherapy, to enhance immunogenic cell death and improve cancer therapy. The review also highlights the potential of PDT in inducing immune memory and preventing cancer recurrence. Despite the promising results, further research is needed to optimize PDT protocols and address the limitations of the TME.