The study tested a hypothesis, based on the cognitive dissonance theory, that not only stimulus and response conflicts, as studied to date on the grounds of the influential conflict monitoring theory of human self-control, but also semantic incompatibility between complex cognitive representations, can mobilize such self-control.In two experiments, we applied a realistic task (simulated web feed), and manipulated the amount of semantic conflict (contradictory text messages), as well as the amount of tempting distractors (jokes and erotic pictures) that were supposed to be ignored. Experiment 1 demonstrated that semantic conflict mobilized self-control, as evidenced by participants better ignoring distraction. Experiment 2 showed that semantic conflict yielded the self-control depletion effect, analogous to the effects caused by a prolonged resistance to distraction, most probably because it mobilized self-control. The results extend the conflict monitoring theory, by implying that the detection of cognitive dissonance between incoming messages can also serve to regulate the strength of self-control.