During the past two decades, our understanding of oncogenesis has advanced considerably and many new signalling pathways have been identified. Differences in signalling events that distinguish normal cells from tumour cells provide new targets for the development of anticancer agents. Peptide aptamers are small peptide sequences that have been selected to recognise a predetermined target protein domain and are potentially able to interfere with its function. They represent useful molecules for manipulating protein function in vivo. The isolation and use of specific peptide aptamers as inhibitors of individual signalling components, essential in cancer development and progression, provides a new challenge for drug development. Although peptides make up only a small fraction of current therapeutics, their potential is being enhanced by new developments affecting their modification, stability, delivery and their successful application in preclinical settings. This review summarises the methods that can be used for the isolation and delivery of peptide aptamers, as well as the important achievements that have been made using such peptide aptamers in different systems. The applicability of peptide aptamers as novel cancer therapeutics will be discussed.