Mouse and human dendritic cells (DCs) are composed of functionally specialized subsets, but precise interspecies correlation is currently incomplete. Here, we showed that murine lung and gut lamina propria CD11b⁺ DC populations were comprised of two subsets: FLT3- and IRF4-dependent CD24⁺CD64⁻ DCs and contaminating CSF-1R-dependent CD24⁻CD64⁺ macrophages. Functionally, loss of CD24⁺CD11b⁺ DCs abrogated CD4⁺ T cell-mediated interleukin-17 (IL-17) production in steady state and after Aspergillus fumigatus challenge. Human CD1c⁺ DCs, the equivalent of murine CD24⁺CD11b⁺ DCs, also expressed IRF4, secreted IL-23, and promoted T helper 17 cell responses. Our data revealed heterogeneity in the mouse CD11b⁺ DC compartment and identifed mucosal tissues IRF4-expressing DCs specialized in instructing IL-17 responses in both mouse and human. The demonstration of mouse and human DC subsets specialized in driving IL-17 responses highlights the conservation of key immune functions across species and will facilitate the translation of mouse in vivo findings to advance DC-based clinical therapies.