Calculations were carried out to analyze the strain dependence of the binding energy of a carbon adatom deposited on a (2 x 1) dimerized Si(100) surface. Two different low energy binding sites on the reconstructed Si(100) surface were taken into consideration. The lowest energy site is located near the top position of a second layer Si atom; while the second lowest energy site is at the bridge site between two top layer Si atoms forming the dimer. Results indicate that the binding energy for a carbon atom adsorbed in the lowest energy sites is affected most by the esxternal strain. In particular, the effect of a uniaxial strain applied in the direction perpendicular to the surface Si dimers, was found to be quite significant. While a tensile stress in this direction produces an increase in the value of the binding energy, a compressive strain was found to lower the binding energy. In general, strains applied in the direction parallel and perpendicular to Si dimers were found to produce opposing effects on the binding energies.