Previous studies showed that the barrier properties of nanocomposites based on nanoplatelets depend significantly on nanoplatelets orientation. Despite its significant importance, only numerical simulations and empirical models have been presented for prediction of the effect of nanoplatelets orientation on gas permeability of polymer nanocomposites. In this work, an analytical model that predicts the gas permeability of polymer nanocomposite containing nanoplatelet particles is presented. The model considers particle orientation and requires particles volume fraction and aspect ratio. In order to examine model predictions, film samples of aromatic polyamide and organoclay nanocomposite were prepared using cast extrusion. Orientation of the organoclay nanoplatelets was determined using Fourier Transformed Infrared spectroscopy and their permeability to oxygen was measured. Model predictions were compared with the experimental results and previous results reported in literature. It is shown that the proposed model can predict permeability of nanoplatelet nanocomposites with a higher degree of precision compared to the previous empirical equation in the literature.