Gas separation methods have received much attention, as the process plays a key role in various industries. Among the gas separation methods, membrane-based methods, particularly those employing mixed matrix membranes (MMMs), are important. MMMs are formed by modifying the properties of polymeric membranes by fabricating them with inorganic particles. This paper presents the gas transport behaviour in MMMs fabricated with porous particles, as described by two-phase (ideal) and three-phase (non-ideal) models. The effect of particle porosity on gas permeability was incorporated into existing models through the J parameter, which adjusts the particle loading percentage. J-modified models were verified against existing models and experimental data for gas permeability were obtained with various MMMs. It was found that the proposed modified models provide a better prediction of the gas transport behaviour in MMMs.