The exploration of Nd and Eu precursors bearing the (form-)amidinate ligand for atomic layer deposition (ALD) with water resulted in crystalline Nd₂O₃ and Eu₂O₃ thin films on Si substrates at low temperatures. Eu₂O₃ films exhibit strong photoluminescence with well-defined ⁵D₀ → ⁷F_j transitions that evolve from surface-dominated to bulk-like emission as thickness increases, approaching the optical quality of single crystals. In contrast, Nd₂O₃ shows temperature-dependent visible emission from defect states rather than f–f transitions, while controlled nitrogen incorporation at 350 °C induces room-temperature luminescence through defect engineering. Leveraging the high reactivity of the Nd and Eu precursors, which was predicted and confirmed by density functional theory (DFT) studies, atomic and molecular layer deposition (ALD/MLD) experiments using −OH and −NH₂ containing organic coreactants were performed. Using terephthalic acid (TPA) as a coreactant resulted in high growth per cycle (GPC) values (3.1 Å for Nd-TPA and 3.3 Å for Eu-TPA). Additionally, adenine, guanine, and melamine were successfully introduced as organic linkers, along with rare-earth (RE) precursors. Besides reporting promising water-assisted ALD processes for Nd₂O₃ and Eu₂O₃ thin films, this study broadens the range of RE-organic materials available and highlights the importance of designing targeted precursors.