The structure of 1,2-dichloroethane (DCE) adsorbed on Cu(111) in a single monolayer form has been investigated using ClK-edge near-edge X-ray absorption and normal-incidence standing X-ray wavefield absorption at the (111) reflection. These measurements indicate a small tilt (25°) of the ClC axis from parallel to the surface, and two different equally occupied ClCu layer spacings relative to the extended lattice planes of 1.0 and 1.6 Å. These resutls are found to be best reconciled with a structural model in which the DCE bonds with the ClCCCl plane of the trans conformer perpendicular to the surface and the Cl atoms over atop adsorption sites, the CuCl bondlength being compatible with the van der Waals radius for Cl. The possible role of a frustrated rotational mode of the adsorbed molecule leading to a “flipping” between two equivalent states is considered.