Cell-penetrating peptides (CPPs) as carriers for the intracellular delivery of various proteins and macromolecules have been studied extensively. Nonetheless, the delivery efficiency is relatively low. We showed previously that a rigid and fibrous cationic coiled-coil protein, CCPC 140, has cell-penetrating activity superior to that of reported CPPs. In this report, we exploited CCPC 140 for the intracellular delivery of the green fluorescent protein (GFP). The activity of CCPC 140 for intracellular delivery of GFP was compared with an octa-arginine peptide, a typical CPP that is widely used. The cellular delivery of proteins by CCPC 140 was >20-fold more efficient than that of octa-arginine. These results indicate that CCPC 140 has significant potential for delivery of proteins to cells.