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A combination of biomedical and technological applications is generating, over the past decades, the well-established interest toward melanins and melanogenesis. Several compounds have been explored to promote/catalyze oxidative polymerization of melanogenic precursors, such as 5,6-dihydroxyindole-2-carboxylic acid (DHICA), to melanin-like biopolymers in vitro. TiO2 has shown a photocatalytic activity driving DHICA polymerization and leading to the formation of melanin–TiO2 hybrid nanostructures with unique biocide behavior even under visible light. However, the mechanism of melanin formation in those hybrids is not yet well understood although a ligand to metal charge transfer (LMCT) process involving DHICA and Ti4+ ions was hypothesized. Here, we focus on melanin formation and apply a complementary analysis, by using photoluminescence (PL), UV–vis, electron paramagnetic resonance (EPR), and nuclear magnetic resonance (NMR) spectroscopy to reveal the mechanism of DHICA polymerization in the presence of a TiO2-sol. This study discloses TiO2 potentialities to drive and template DHICA polymerization to melanin via LMCT-based photo-oxidative process.