The adhesion properties of a thermoplastic olefin elastomer (TPO) after ozone exposure are studied with attenuated total reflection infrared spectroscopy (ATR), the lap shear test, and contact angle measurement. The ozone treatment is applied after the TPO is dip-coated with acrylic acid (AA) that is mixed with benzophenone, benzoyl peroxide (BPO), and azobisisobutyronitrile initiators. ATR spectra confirm the presence of grafted AA on TPO, the amount of which depends on the ozone exposure lime and the type of initiator applied. The total surface energy, the polar component, and lap shear strength (LSS) of the grafted TPO increase with increasing ozone exposure time and also vary with the initiator. All AA-grafted TPOs have much greater LSS than the TPO without AA. The greatest LSS is obtained from the specimen grafted with AA and BPO. In addition, the small differences in surface energies and failure strains associated with the great changes in LSS obtained from various specimens implies that the nature of the grafted layer has a significant effect on the adhesion strength.