We prepared poly(vinyl alcohol) (PVA)/SiO2 and PVA/SiO2/glutaraldehyde (GA) nanocomposite membranes in a single step using the solution casting method. The structure, morphology, and properties of these nanocomposite membranes were characterized by Raman spectroscopy, atomic force microscopy, small- and wide-angle X-ray scattering, thermogravimetric analysis, differential scanning calorimetry, and dynamic mechanical analysis (DMA). The influence of silica and GA loading on the meso-scale characteristics of the composite membranes was investigated. The results showed that silica deposited in the form of small nanoparticles (similar to 1 nm) in the PVA/SiO2 membranes, while bigger submicron particles (>25 nm) were formed in the PVA/SiO2/GA membranes. The water uptake of the PVA/SiO2 membranes increased with temperature, but the PVA/SiO2/GA membranes were completely dissolved above 50 degrees C. We can therefore conclude that the addition of GA deteriorated the properties of PVA/SiO2 membranes. The thermal stability of the PVA/SiO2 membranes increased with the increasing silica loading with a maximum char yield of 46 % for PVA/SiO2/4T. Even DMA profiles indicated a promising increase in E-R (rubbery modulus) from 6 MPa (PVA membrane) to 1015 MPa (PVA/SiO2/4T) at 250 degrees C, showing high mechanical strength of these membranes.