Terahertz (THz) technology has emerged for biomedical applications such as scanning, molecular spectroscopy, and medical imaging. However, the biological effect of THz radiation is not fully understood. Non-thermal effects of THz radiation were investigated by applying a femtosecond-terahertz (fs-THz) pulse to mouse skin. Analysis of the genome-wide expression profile in fs-THz-irradiated skin indicated that wound responses were predominantly through NFκB1- and Smad3/4-mediated transcriptional activation. Repeated fs-THz radiation delayed the closure of mouse skin punch wounds due to up-regulation of transforming growth factor-beta (TGF-β). These findings suggest that fs-THz radiation provokes a wound-like signal in skin with increased expression of TGF-β and activation of its downstream target genes, which perturbs the wound healing process in vivo. To identify non-thermally induced in vivo mode action of THz radiation, gene expression profile of fs-THz-irradiated skin (at post 24-hours after 1 hour exposure) was explored. Purified total RNAs from independent 3 mice of each sham and THz group were labeled and hybridized on the Mouse Gene 1.0 ST Array (Affymetrix, Santa Clara, CA), according to manufacturer's standard protocol. Statistically filtered THz-responsive genes were examined for possible interactions with other molecules, canonical signaling pathways, and bio-functions.