Aim: To identify a novel antiviral peptide against dengue virus serotype 2 (DENV-2) by screening a phage display peptide library and to evaluate its in vitro antiviral activity and mode of action. Methods and Results: A phage display peptide library was biopanned against purified DENV-2 and resulted in the identification and selection of a peptide (peptide gg-ww) for further investigation. ELISA was performed, and peptide gg-ww was shown to possess the highest binding affinity against DENV-2. Thus, peptide gg-ww was synthesized for cytotoxicity and antiviral assays. Virus plaque reduction assay, real-time PCR and immunofluorescence assay were used to investigate the inhibitory effect of peptide gg-ww on DENV-2 infection in Vero cells. Three different assays (pre-, simultaneous and post-treatments assays) were performed to investigate the peptide's mode of action. Results indicated that peptide gg-ww possessed strong antiviral activity with a similar to 96% inhibition rate, which was achieved at 250 mu mol l(-1). Viral replication was inhibited during a simultaneous treatment assay, indicating that the entry of the virus was impeded by this peptide. Conclusions: Peptide gg-ww displayed antiviral action against DENV-2 by targeting an early stage of viral replication (i.e. during viral entry). Significance and Impact of the Study: Peptide gg-ww may represent a new therapeutic candidate for the treatment of DENV infections and is a potential candidate to be developed as a peptide drug.