The rate coefficient and the thermal cross section for the oxygen ion–ion dissociative recombination are calculated using the semiclassical formalism. The motion of the heavy particles (positive and negative ions) in their mutual Coulomb field is treated classically. At certain ranges of the ion–ion separation (determined from energy conservation), the electron tunnels from the negative ion to the positive ion. Using the experimental data on the electron binding energy of O2−, this tunneling effect is calculated in the WKB approximation. It is found that the linewidth of the levels due to the dissociative effect is important for the electron tunneling and the molecular dissociation. The rate coefficients and the thermal cross sections have been calculated between 200° and 500°K, and have the orders of magnitude 10−8 − 10−7 cm3/sec and 10−12 cm2, respectively. We find that they both decrease as the temperature increases, and have the following approximate relations: α∝T−1/2, σ(th) ∝T−1. No direct laboratory data is available, but the theoretical results are in agreement with indirect observations from the ionosphere.