A theory for an electrode-associative ionic fluid interface is proposed. It takes into account the effect of interionic pairing as well as packing and electrostatics. The theory is based on the use of Wertheim's two-density formalism, i.e., the ions are represented as free and associated into dimers. Dimerization is made possible by the attractive interaction between sites embedded in each ion. The results for ionic density profiles calculated in a generalized exponential approximation are given. Analytical expressions for the differential capacitance, potential drop and adsorption coefficient calculated in the mean spherical approximation are presented.