Task performance suffers when an aspect of a stimulus is associated with an incorrect response, thereby evoking cognitive conflict. Such impairment is reduced after recent or frequent conflict occurrence, suggesting attentional adjustment. We examined adjustment to conflict evoked by a temporarily irrelevant S-R rule when participants frequently switched between two semantic classification tasks by manipulating the proportion of conflict trials in one of them. Controlling stimulus-specific presentation frequencies, we found reduced conflict effects under conditions of a higher proportion of conflict trials in the task to which the manipulation was applied, whereas there was no such effect in the other task. Additional analyses demonstrated task-specificity regarding trial-to-trial conflict adjustment. Because conflict was evoked in the absence of perceptually distinct target and distractor stimulus features, these adjustment effects cannot be attributed to perceptual selection.