The grand canonical Monte Carlo (GCMC) simulation technique is used to study water adsorption and condensation in a realistic Vycor-like silica mesoporous system at various temperatures. Water–water interactions are described using the SPC model while water–silica interactions are calculated in the framework of the PN-TrAZ model. Thermodynamic quantities (namely water adsorption isotherms and isosteric heat of adsorption curves) have been calculated along with water–water and water–Vycor pair distribution functions. The simulated adsorption isotherm at room temperature compares well with published experimental data. Isosteric heat curves are characteristic of adsorption in a heterogeneous environment. We also show that the BET method for specific surface determination is not valid in the case of water confined in silica mesoporous materials. By analysing water–water and water–Vycor pair correlation functions, we demonstrate the existence of strong distortion compared to bulk water due to the influence of the silica surface. The hydrogen bond is significantly elongated and angle distorted.