Peptide-based drug delivery systems (PDCs) are promising for targeted drug delivery, improving bio-compatibility and physiological stability. Peptides, with high affinity, low immunogenicity, and adjustable molecular size, can be coupled to drugs via linkers to form PDCs, which are effective in delivering therapeutic agents like anti-cancer drugs and nucleic acids. PDCs enhance drug concentration at target sites, reduce toxicity, and prolong drug half-life. This review discusses recent advancements in functional peptide-based DDSs, focusing on cell-targeting peptides, cell-penetrating peptides, and environment-stimulus-responsive peptides. Cell-targeting peptides, such as RGD, NGR, and EGFR, bind to specific receptors on tumor cells, enhancing drug delivery and therapeutic efficacy. Cell-penetrating peptides (CPPs) facilitate drug entry into cells through direct translocation or endocytosis. Functional peptides can be modified to form supramolecular hydrogels, enhancing drug delivery and targeting. PDCs have shown promise in clinical applications, including cancer treatment, by improving drug targeting and reducing side effects. Peptide-based DDSs are also being explored for imaging and therapy, with applications in MRI, PET, and fluorescence imaging. Overall, functional peptides offer a versatile platform for targeted drug delivery, with potential for future clinical applications.Peptide-based drug delivery systems (PDCs) are promising for targeted drug delivery, improving bio-compatibility and physiological stability. Peptides, with high affinity, low immunogenicity, and adjustable molecular size, can be coupled to drugs via linkers to form PDCs, which are effective in delivering therapeutic agents like anti-cancer drugs and nucleic acids. PDCs enhance drug concentration at target sites, reduce toxicity, and prolong drug half-life. This review discusses recent advancements in functional peptide-based DDSs, focusing on cell-targeting peptides, cell-penetrating peptides, and environment-stimulus-responsive peptides. Cell-targeting peptides, such as RGD, NGR, and EGFR, bind to specific receptors on tumor cells, enhancing drug delivery and therapeutic efficacy. Cell-penetrating peptides (CPPs) facilitate drug entry into cells through direct translocation or endocytosis. Functional peptides can be modified to form supramolecular hydrogels, enhancing drug delivery and targeting. PDCs have shown promise in clinical applications, including cancer treatment, by improving drug targeting and reducing side effects. Peptide-based DDSs are also being explored for imaging and therapy, with applications in MRI, PET, and fluorescence imaging. Overall, functional peptides offer a versatile platform for targeted drug delivery, with potential for future clinical applications.