To co-express multiple target proteins, we engineered a single-component chimeric tobacco mosaic virus (TMV)-based vector containing homologous and heterologous capsid protein subgenomic RNA promoters. Delivery of this vector into Nicotiana benthamiana plants via agroinfiltration resulted in co-expression of two reporter genes within a single cell. Furthermore, co-expression of a host-specific antisense RNA or a silencing suppressor protein from this vector augmented the accumulation of green fluorescent protein or a vaccine antigen, hemagglutinin from avian influenza virus A/Vietnam/1194/04. These findings suggest that this chimeric vector utilizing the homologous and heterologous subgenomic TMV promoters has a potential for high-level production of multiple therapeutic proteins including monoclonal antibodies.