Two experiments were conducted to examine effect of afterwarning of communicator's persuasive intent on persuasion and its mediating mechanism under the postulation that afterwarning would produce the persuasion inhibiting effect when a temporal delay between the afterwarning and the measurement of persuasive effect was introduced and thus there was enough time for recipients to engage retroactive counterargumentation to the preceding persuasive communication. Results showed that afterwarning produced resistance to persuasion in the interfered-thought conditions in Experiment 2 and potential resistance to persuasion in psychological processes in the temporal delay conditions in Experiment 1 and in the indicated-thought conditions in Experiment 2. Results also showed that, as mediating mechanism of the persuasion inhibiting effect of afterwarning, negative thoughts (retroactive counterarguments) played the most important role in the temporal delay conditions in Experiment 1 and in the indicated-thought conditions in Experiment 2, and that source derogation (Experiment 1 and 2) and psychological reactance (Experiment 1) played some role, too. Finally, it was interpreted that not only to present afterwaming but also to recommend thinking over the persuasion from a negative viewpoint was effective as defensive method against undesirable preceding persuasion attack.