The iron incorporated mesoporous Al2O3-MCM-41 nanocomposites, synthesized by sol gel and followed by wetness impregnation method, were found to be active photocatalysts for evolution of hydrogen energy from water in the presence of sacrificial agent under visible light illumination (lambda >= 400 nm). The key factors for water splitting are appropriate band gap energy, small particle size, high surface area and mesoporosity nature. The DRUV-vis spectra measured the band gap energy where as the particle sizes of the materials were evaluated by TEM. Beside these, the materials were characterized by small angle XRD, N-2 adsorption-desorption, FTIR and XPS. Moreover, among mesoporous support and mesoporous nanocomposites, 5Fe/Al2O3-MCM-41 exhibited highest water splitting ability and produced 146 mu mol/h hydrogen gas with apparent quantum efficiency 6.1%. The textural properties (high surface area, narrow pore size, large pore volume and mesoporosity), visible light active band gap energy 1.90 eV and small particle size (47.95 nm) collectively contribute for high hydrogen production ability of 5Fe/Al2O3-MCM-41. Copyright (C) 2011, Hydrogen Energy Publications, LLC. Published by Elsevier Ltd. All rights reserved.