Diffusion coefficient of oxygen penetrating into polystyrene (PS) latex/poly (N-isopropylacrylamide) (PNIPAM) microgel composite films were measured using Fluorescence technique. Three different (5, 15, and 40wt%) PS content films were prepared from PS/PNIPAM mixtures. Diffusivity of PS/PNIPAM composite films were studied by diffusion measurements which were performed over the temperature range of 24-70 degrees C. Pyrene was used as the fluorescent probe. The diffusion coefficients (D) of oxygen were determined using the SternVolmer fluorescence quenching method combined with Fickian transport and were computed as a function of temperature for each PS content film. The results showed that D values were strongly dependent on both temperature and PS content in the film. Diffusion energies were measured and found to be dependent on the composition of the composite films. Copyright (C) 2011 John Wiley & Sons, Ltd.