Accurate diagnosis of influenza viruses is difficult and generally requires a complex process because of viral diversity and rapid mutability. In this study, we report a simple and rapid strategy for the detection and differentiation of influenza viruses using glycan-functionalized gold nanoparticles (gGNPs). This method is based on the aggregation of gGNP probes on the viral surface, which is mediated by the specific binding of the virus to the glycans. Using a set of gGNPs bearing different glycan structures, fourteen influenza virus strains, including the major subtypes currently circulating in human and avian populations, were readily differentiated from each other and from a human respiratory syncytial virus in a single-step colorimetric procedure. The results presented here demonstrate the potential of this gGNP-based system in the development of convenient and portable sensors for the clinical diagnosis and surveillance of influenza viruses.