A bovine derived antimicrobial peptide, indolicidin (IL), was studied of its new application for gene transfer. Plasmid DNA was complexed with both IL and polyethylenimine (PEI) as ternary particles. Compared to DNA/IL complexes, the DNA/IL/PEI particles demonstrated high zeta potentials, small particle sizes, and superior loading efficiencies, suggesting the incorporation of polycations can support IL for gene delivery. For in vitro experiments, these ternary particles significantly improved gene transfection efficiencies over the sole administrations of IL or PEI. This synergistic effect revealed that IL and PEI may play different roles for gene transfer. Our results suggest that IL should be a potential carrier for gene delivery. As our knowledge, our study should be the first article indicating the carrier ability of IL for gene transfer.