A new low temperature atomic layer deposition (LT-ALD) Al2O3 process using trimethylaluminum (TMA) and acetic acid (CH3COOH) is studied both theoretically and experimentally. The atomistic mechanisms of the two deposition half-cycles on Al-CH3*, Al-OH*, and Al(η2-O2CCH3)* are investigated using density functional theory (DFT). The experimental demonstrations are performed on Si substrates over the growth temperature range 75–400°C. Consistent with the DFT simulation, lower linear growth rate and shorter required oxidant purge times are observed at 90°C, when compared to LT-ALD Al2O3 using H2O as the oxidant. The chemical characteristics of the Al2O3 films grown with both CH3COOH at 90°C and H2O at 100°C are determined and compared using X-ray photoelectron spectroscopy (XPS).