Recent research has suggested that when people resist persuasion they can perceive this resistance and, under specifiable conditions, become more certain of their initial attitudes (e.g., Z. L. Tormala & R. E. Petty, 2002). Within the same metacognitive framework, the present research provides evidence for the opposite phenomenon—that is, when people resist persuasion, they sometimes become less certain of their initial attitudes. Four experiments demonstrate that when people perceive that they have done a poor job resisting persuasion (e.g., they believe they generated weak arguments against a persuasive message), they lose attitude certainty, show reduced attitude-behavioral intention correspondence, and become more vulnerable to subsequent persuasive attacks. These findings suggest that resisted persuasive attacks can sometimes have a hidden yet important success by reducing the strength of the target attitude.