Purpose <p>The current study applies a Quality by Design strategy to design and optimise a Diosmetin-loaded transferosome (DM-TR) gel for transdermal therapy of melanoma, a skin cancer.</p> Method <p>QbD tools including Ishikawa diagram, Risk Estimation Matrix, and Failure Mode Effect Analysis were used to construct the Quality Target Product Profile, identify Critical Quality Attributes, and conduct risk assessments. Design of experiments was applied to establish the design space. Transferosomes were evaluated for vesicle size, zeta potential, entrapment efficiency, surface morphology, deformability index, and in-vitro drug release. A DM-TR gel was prepared using carbopol 934 and assessed for physicochemical properties, skin penetration, deposition, dermal toxicity, cytotoxicity (B16-F10 cell line), and stability under ICH conditions.</p> Results <p>Optimised transferosomes showed desirable size, entrapment efficiency and stability with effective in-vitro release. The DM-TR gel exhibited suitable physical characteristics, enhanced skin penetration and deposition, significant cytotoxicity against melanoma cells compared to plain diosmetin.</p> Conclusion <p>The findings support DM-TR gel as a promising transdermal delivery system for melanoma therapy.</p> Graphical Abstract <p></p>