Streptococcus pneumoniae (the pneumococcus) is a leading cause of pneumonia in children under five years old. Co-infection of pneumococci with respiratory viruses enhances disease severity. Most studies investigating pneumococcal-viral co-infection have focused on lower respiratory tract infections. However, both pneumococci and respiratory viruses colonise the upper respiratory tract (the nasopharynx), which serves as a pre-cursor to disease and a reservoir for host-to-host transmission of these microbes. Although pneumococcal-influenza co-infections have been well investigated, less is known about pneumococcal co-infections with Respiratory Syncytial Virus (RSV), a major cause of bronchiolitis in infants under two years old. In this study, we developed an infant mouse co-infection model using Pneumonia Virus of Mice (PVM, a murine analogue of RSV), and demonstrated that PVM infection increases pneumococcal nasopharyngeal density, and shedding in nasal secretions, but not acquisition of pneumococci by naive hosts. These data suggest the virus enhances the early stages of pneumococcal transmission but not the later stages. Unexpectedly, we also identified that mice colonised with pneumococci exhibit a reduction in viral loads 11 days post-PVM. This effect was not dependent on pneumococcal strain, and occurred regardless of the order of infection. Examination of viral loads over time revealed that the pneumococcal-mediated reduction in viral loads was caused by accelerated clearance of the virus from the nasopharynx. Cytometric bead arrays revealed co-infected mice also had higher levels of pro-inflammatory chemokine Mip-1α compared to mock or mono-infected mice, which is known to play a role of viral clearance. While the consensus in the field is that pneumococcal-viral co-infection is synergistic, our study has uncovered that aspects of the relationship are antagonistic. Future studies will focus on uncovering the mechanism of this antagonism and the public health implications of our findings for bacterial and viral vaccination strategies in young children.