We report results from a study of events with a leading antiproton of beam momentum fraction 0.905<0.965 and 4-momentum transfer squared |t|<3GeV2 produced in p¯p collisions at s√=1800GeV at the Fermilab Tevatron collider. Approximately 2% of the events contain two jets of transverse energy EjetT>7GeV. Using the dijet events, we evaluate the diffractive structure function of the antiproton and compare it with expectations based on results obtained in diffractive deep inelastic scattering experiments at the DESY ep collider HERA.