Cell-penetrating peptides have gained attention owing to their promise in noninvasive delivery systems. Among the identified cell-penetrating peptides, the TAT peptide has been preferentially used for transduction into cells of diverse origins. However, this activity is nonselective between neoplastic and non-neoplastic cells. Here we describe artificial cell-penetrating peptides that are selectively and efficiently incorporated into human tumour cells, according to their lineage. Ten representative tumour lineage-homing cell-penetrating peptides were obtained by screening of a random peptide library constructed using messenger RNA display technology, and some of the isolates were further modified by amino-acid substitution. Their advantageous tumour cell-targeting ability is corroborated in an in vivo mouse model for imaging and growth suppression of metastatic xenoplant tumours. These cell-penetrating peptides are potentially useful for the efficient targeting of human neoplasms in a tumour origin-dependent manner, and provide a framework for the development of peptide-based anti-tumour technologies.