The pathogen Streptococcus pneumoniae (the pneumococcus) is a significant cause of mortality and morbidity worldwide. Acquisition and subsequent nasopharyngeal colonization by pneumococci are essential prerequisites for invasive disease. However, the mechanics of pneumococcal transmission events have been poorly characterized. Established models are not robust enough to undertake genetic screens due to small number of bacteria that both transmit and can be recovered. Ferrets have long been used to model transmission of influenza viruses through both contact dependent and aerosol routes. Seasonal dynamics of pneumococcal colonization support a role of influenza in transmission of pneumococci. This study describes a model of pneumococcal transmission in influenza co-infected ferrets. Transmission of pneumococcus was highly dependent on influenza strain used, suggesting a role of viral factors in either pneumococcal shedding or acquisition. Using a highly saturated transposon library, we recovered sufficient bacterial libraries from directly infected (index) and contact ferrets to determine the bottlenecks of transmission. These data was further leveraged to identify putative bacterial factors necessary for transmission of the pneumococcus. These data represent the first genetic screen in pneumococcus for bacterial factors required for transmission in mammalian hosts.