In this work, high density polyethylene (HDPE)/organo-clay (Cloisite® 15A) nanocomposites with different types of compatibilizer and having various clay amount and compatibilizer/clay weight ratio were prepared by melt blending in a batch, internal mixer. Poly(ethyleneco- metacrylic acid) Na+ salt, poly(ethylene-co-acrylic acid) and poly(ethylene-g-maleic anhydride) copolymers were used as compatibilizer. Film samples were prepared by hot compression. Clay dispersion was investigated by X-Ray diffraction (XRD) and Transmission Electron Microscopy (TEM) methods. Viscoelastic behavior of the nanocomposites was analyzed by a dynamic oscillatory rheometer in the melt state. Oxygen permeability properties of the samples were tested with a gas permeability tester. Degree of crystallinity was calculated by XRD and differential scanning calorimetry (DSC) methods. It was found that compatibilizer structure and amount affect the oxygen permeability values of nanocomposite films. Consequently, enhancement in oxygen permeability of the nanocomposite films must be evaluated taking into account of the sample composition, compatibilizer structure, clay dispersion and crystallinity. High barrier, flexible and transparent polyethylene/clay nanocomposite packaging films could be considered as one of the novel innovations in barrier technologies.