Peptides are ideal biologicals for targeted drug delivery and have also been increasingly employed as theranostic tools in treating various diseases, including cancer, with minimal or no side effects. Owing to their receptor-specificity, peptidemediated drug delivery aids in targeted drug delivery with better pharmacological biodistribution. Nanostructured self-assembled peptides and peptide−drug conjugates demonstrate enhanced stability and performance and captivating biological effects in comparison with conventional peptides. Moreover, they serve as valuable tools for establishing interfaces between drug carriers and biological systems, enabling the traversal of multiple biological barriers encountered by peptide−drug conjugates on their journeys to their intended targets. Peptide-based drugs play a pivotal role in the field of medicine and hold great promise for addressing a wide range of complex diseases such as cancer and autoimmune disorders. Nanotechnology has revolutionized the fields of medicine, biomedical engineering, biotechnology, and engineering sciences over the past two decades. With the help of nanotechnology, better delivery of peptides to the target site could be achieved by exploiting the small size, increased surface area, and passive targeting ability of the nanocarrier. Furthermore, nanocarriers also ensure safe delivery of the peptide moieties to the target site, protecting them from degradation. Nanobased peptide delivery systems would be of significant importance in the near future for the successful targeted and efficient delivery of peptides. This review focuses on peptide−drug conjugates and nanoparticle-mediated self-assembled peptide delivery systems in cancer therapeutics.