Conventional dendritic cells (cDCs) are key antigen-presenting cells that initiate antitumor T-cell immunity and represent promising candidates for cellular immunotherapy. However, existing protocols for generating cDCs from CD34+ hematopoietic progenitor cells (HPCs) are primarily optimized for cord blood and are not readily adaptable to clinical manufacturing. Here we developed and optimized a GMP-compliant platform for the generation of cross-presenting cDCs from clinically relevant adult CD34+ HPC sources. Using a two-step culture system incorporating Flt3L, SCF, IL-3, TPO, SR1, GM-CSF, IL-4, and IFN-γ, we generated cDC1 and cDC2 from cord blood, bone marrow, and G-CSF-mobilized peripheral blood CD34+ HPCs. Systematic optimization identified SR1, TPO, and IFN-γ as key factors enhancing cDC1 differentiation, whereas IL-6 inhibited cDC generation. The optimized protocol reproducibly increased cDC1 output while maintaining robust cDC2 generation across all HPC sources, including samples from melanoma patients. CD34-derived cDCs expressed canonical DC markers and upregulated co-stimulatory molecules following activation. Activated cDCs produced high levels of IL-12p70, efficiently cross-presented MART-1 antigen, expanded antigen-specific CD8+ T cells, promoted the differentiation of multifunctional cytotoxic T cells, and enhanced melanoma cell killing in vitro. In conclusion, we established a GMP-compliant platform for generating cross-presenting human cDCs from adult CD34+ HPCs. These cells exhibit potent antigen-presenting and T-cell priming capacity, supporting their development as next-generation dendritic cell vaccines and the further clinical development of cDC-based cancer immunotherapies.