A rotationally resolved near-infrared spectrum has been obtained for the ethylene-CO2 van der Waals complex. The structure obtained for this complex has the carbon dioxide lying above the plane of the ethylene molecule, with the CO2 axis parallel to this plane. The individual subbands observed in the spectrum are shifted from the expected rigid rotor positions, indicative of internal rotation of the two monomer units within the complex. A double rotor model is presented that accounts for the shifts and provides an estimate of the barrier to internal rotation. The results indicate that the complex is completely delocalized along the internal rotational coordinate. Ab initio calculations are also presented that are in good agreement with this picture.