This research explores when and how tailoring messages to attitudinal bases backfires. Study 1 demonstrated that for attitudes (toward education subsidies) that were based more on beliefs than emotions, recipients whose initial attitudes were incongruent with the message position (i.e., message opponents) showed mismatching effects, such that the affective message was more persuasive than the cognitive message. Study 2 replicated these mismatching effects among message opponents for attitudes (toward a rival university) that were primarily affective. Study 3 controlled for effects of initial attitude certainty and replicated the mismatching effects of Study 2 for affective attitudes toward an increase in tuition. Finally, Study 4 suggested a potential mechanism for mismatching effects, revealing that for attitudes (toward an online course management system) that were based more on beliefs than emotions, message opponents counter-argued with the cognitive appeal more intensely than the affective appeal. Contrary to the notion in the extant literature that mismatching effects are relatively rare compared with matching effects, the current research suggests that mismatching effects occur for both primarily affective and cognitive attitudes when the recipient is highly opposed to the message position. The present findings also demonstrate the utility of examining attitudinal bases at the object level in the context of message tailoring. Implications for message tailoring and for affective versus cognitive attitudes are discussed. Copyright © 2013 John Wiley & Sons, Ltd.