Abstract Although CD4+ T cell help (Th) is critical for inducing optimal B cell and CD8+ T cell responses, it remains unclear whether induction of CD4+ Th responses postinfection are also dependent on CD4+ T cell help. In this study, we show that activation of adoptively transferred Th cells during primary influenza A virus (IAV) infection enhances both the magnitude and functional breadth of endogenous primary IAV-specific CD4+ T cell responses. This enhancement was dependent on CD154-CD40–dependent dendritic cell licensing and resulted in a greater recall capacity of IAV-specific CD4+ and CD8+ T memory responses after heterologous IAV infection. These data suggest that engaging pre-existing CD4 responses at the time of priming may be a strategy for improving cellular immunity after vaccination.