This study aimed to identify a new skin penetrating peptide (SPP) able to enhance unfractionated heparin (UFH) permeation through human epidermis by screening a phage display peptide library. The effects of the synthesized heptapeptide (DRTTLTN) on human stratum corneum organization were investigated by ATR-FTIR spectroscopy and molecular dynamics simulation. The DRTTLTN penetration within the human epidermis caused both a fluidization of the stratum corneum lipids and the extension of keratins due to the increase of the contribution of α-helices. The coadministration of DRTTLTN with UFH resulted ineffective in increasing skin penetration due to UFH affinity for keratins. The conjugation of DRTTLTN to UFH by N-(3-(dimethylamino)propyl)-N'-ethylcarbodiimide hydrochloride and sodium N-hydroxysulfosuccinimide led to an increase of the flux of 24-36-fold with respect to raw UFH, depending on the adopted synthetic procedure. The new compounds showed a decrease of the antifactor Xa activity of about 4-5 times. DRTTLTN also permitted to increase the fluxes of small model molecules. In conclusion, these data support the use of SPP to enhance the skin penetration of poorly absorbed compounds even in the case of macromolecules as polysaccharides.