<p>Bioactive compounds extracted from apple mango leaf exhibit notable phytochemical, biological, and pharmacological properties, including antioxidant and immunomodulatory effects, supporting their broad application potential. We investigated the immunomodulatory potential of apple mango leaf extract (AMLE) on bone marrow-derived dendritic cells (BMDCs) using integrated RNA-sequencing and assay for transposase-accessible chromatin with sequencing analyses, validated by flow cytometry. Weighted gene co-expression network analysis (WGCNA) identified key gene modules that were differentially expressed following AMLE treatment. Specifically, upregulated modules were highly enriched in the NF-κB, mitogen-activated protein kinase (MAPK), and PI3K signaling pathways, as well as in robust immune activation. Integrative transcriptomic and chromatin accessibility analyses revealed that AMLE treatment upregulated <i>Il1b</i>, <i>Flt3</i>, and <i>Irf8</i>, which was accompanied by increased accessibility of PU.1- and ETS1-binding motifs. Notably, AMLE consistently downregulated cell cycle-related transcription factors (e.g., the E2F family), indicating a shift from an immature proliferative state to functional maturity, with <i>Il1b</i> emerging as a central regulator of transcriptional and epigenetic responses. Flow cytometry confirmed that AMLE enhanced the maturation of MHCII⁺CD11c⁺CD11b^lo BMDCs, as evidenced by elevated MHCII, CD40, and CD80 expression. Crucially, pharmacological inhibition of PU.1 using DB1976 effectively abrogated this maturation, identifying PU.1 as an indispensable driver of AMLE-mediated DC activation. Therefore, AMLE induced concerted transcriptional and chromatin-remodeling events that drove DC activation. Overall, AMLE enhances DC maturation through the <i>Il1b</i>–PU.1 regulatory network, highlighting its potential as a natural immunomodulatory agent. </p>