The effects of the polyhedral oligomeric silsequioxanes (POSS) in stacked poly(methyl methacrylate) (PMMA) film samples were investigated in two different film thicknesses, ~50 and ~660 nm. The types of the POSS include methacryl-, octaisobutyl-, and octasilane-POSS. The glass transition temperature (Tg) and isothermal physical aging was depressed by the reduction of film thickness. Among POSS molecules used in this work, methacryl-POSS was the greatest effect in both Tg and relaxation enthalpy (DHRelax) due to the physical aging. The Kohlrausch-Williams-Watts (KWW) relaxation function was used to further understand the effect of POSS and film thickness on the physical aging.