Atomic iodine desorption from single crystal nickel surfaces, Ni(100) and Ni(111), has been monitored by temperature-programmed desorption (TPD). CF3I was used as a precursor molecule for iodine adsorption. At low coverages, theta(iodine) = 0.016 ML, the temperature of the desorption rate maximum (T-max) is near 1035 K for desorption from Ni(100) whereas at higher coverages, theta(iodine) = 0.20 ML, the temperature decreases to 970 K. There is a similar decrease in T-max with increasing coverage for iodine desorption from Ni(111). Analysis of the TPD data shows that iodine desorption follows first-order reaction kinetics with a coverage-dependent activation energy. We have modeled the coverage-dependent activation energy of desorption, E(des)(theta), in terms of a repulsive dipole-dipole interaction, E(dip)(theta), in the adsorbed layer, where E(des)(theta) = E(des)(theta = 0) - E(dip)(theta). The activation energy of desorption at low coverages, E(des)(theta = 0), was determined to be 249 and 214 kJ/mol from Ni(100) and Ni(111), respectively. The activation energy decreases by approximately 7% in the coverage range studied, theta = 0 - 0.20 ML. Simulated desorption curves agree well with the experimental data.