Peptide-based nanosystems for photodynamic therapy (PDT) offer versatile and effective strategies for targeted cancer treatment. PDT uses photosensitizers (PSs) to generate reactive oxygen species (ROS) under light, which can destroy cancer cells. Peptides, due to their stability, low cost, and tunable properties, are increasingly used as targeting ligands and functional components in PDT. They can be modified to enhance targeting, stimuli responsiveness, self-assembly, and therapeutic activity. Peptide-based nanosystems can be designed for various functionalities, including targeted delivery, stimuli-responsive release, self-assembly, and therapeutic applications. Peptides can be linear or cyclic, with different sequences and modifications affecting their properties. They can be used to target specific receptors or organelles, such as the plasma membrane, mitochondria, or ER. Stimuli-responsive peptides can respond to environmental cues like pH, ROS, or enzymes, enabling controlled drug release. Self-assembled peptide nanosystems can form stable structures that enhance tumor targeting and therapeutic efficacy. Examples include nanocarriers like polymeric nanoparticles, liposomes, and hydrogels, which can deliver PSs and drugs to tumor sites. Recent advances in peptide-based PDT include the development of multifunctional nanosystems that combine targeting, stimuli responsiveness, and therapeutic activity. These systems can improve PDT efficiency by enhancing drug delivery, reducing side effects, and enabling synergistic therapies. For instance, pH-responsive and light-responsive nanosystems have been designed to release PSs in tumor environments, while self-assembled nanosystems can improve tumor accumulation and stability. Peptide-based nanosystems also show promise in immunotherapy by inducing immunogenic cancer cell death (ICD) and enhancing antitumor immune responses. Overall, peptide-based nanosystems represent a promising approach for PDT, offering precise targeting, controlled release, and enhanced therapeutic outcomes. Their versatility and adaptability make them valuable tools for developing next-generation cancer therapies.Peptide-based nanosystems for photodynamic therapy (PDT) offer versatile and effective strategies for targeted cancer treatment. PDT uses photosensitizers (PSs) to generate reactive oxygen species (ROS) under light, which can destroy cancer cells. Peptides, due to their stability, low cost, and tunable properties, are increasingly used as targeting ligands and functional components in PDT. They can be modified to enhance targeting, stimuli responsiveness, self-assembly, and therapeutic activity. Peptide-based nanosystems can be designed for various functionalities, including targeted delivery, stimuli-responsive release, self-assembly, and therapeutic applications. Peptides can be linear or cyclic, with different sequences and modifications affecting their properties. They can be used to target specific receptors or organelles, such as the plasma membrane, mitochondria, or ER. Stimuli-responsive peptides can respond to environmental cues like pH, ROS, or enzymes, enabling controlled drug release. Self-assembled peptide nanosystems can form stable structures that enhance tumor targeting and therapeutic efficacy. Examples include nanocarriers like polymeric nanoparticles, liposomes, and hydrogels, which can deliver PSs and drugs to tumor sites. Recent advances in peptide-based PDT include the development of multifunctional nanosystems that combine targeting, stimuli responsiveness, and therapeutic activity. These systems can improve PDT efficiency by enhancing drug delivery, reducing side effects, and enabling synergistic therapies. For instance, pH-responsive and light-responsive nanosystems have been designed to release PSs in tumor environments, while self-assembled nanosystems can improve tumor accumulation and stability. Peptide-based nanosystems also show promise in immunotherapy by inducing immunogenic cancer cell death (ICD) and enhancing antitumor immune responses. Overall, peptide-based nanosystems represent a promising approach for PDT, offering precise targeting, controlled release, and enhanced therapeutic outcomes. Their versatility and adaptability make them valuable tools for developing next-generation cancer therapies.