Can mental imagery rather than external stimulation reactivate an aversive conditioned memory for the purposes of attenuating fear with subsequent extinction training? To answer this question participant underwent a three-day protocol: Day 1 entailed fear acquisition training in which two conditioned stimuli were paired with mild shock (US), while a CS− never was; day 2 included imagery-based reactivation of only one of the two CS+ followed by standard extinction training within the reconsolidation ten minutes later; day 3 included reinstatement by the unsignaled presentation of the US followed by a re-extinction phase. We observed no evidence of fear recovery on the first trial of re-extinction for the reminded, mentally imaged, CS+, whereas fear returned for the non-reminded CS+. Thus, mental imagery was sufficient to reactivate a fear memory thereby opening the reconsolidation window and facilitating fear suppression via extinction training. The clinical implications of this are potentially far-reaching as it allows for in vivo reconsolidation procedures in exposure therapy.