We stapled an amphipathic peptide mainly consisting of leucine (L) and lysine (K) by an azobenzene (Ab) linker for photocontrol of the secondary structure. The cis-trans isomerization of the Ab moieties could stabilize and destabilize the alpha-helical conformation of the LK peptide along with dramatic change of associated peptide structures in a reversible manner by UV-vis irradiation. The cell-penetrating activities of the LK peptide can be readily regulated by the photocontrol, as the stabilized cis-Ab-LK peptide showed remarkable increase of cell penetration compared to the destabilized trans-Ab-LK peptide. The photoswitchable cell-penetrating peptides would provide important structural information for cell permeability as well as an effective targeting strategy for peptide-based pharmaceuticals with spatiotemporal specificity.