Like most strategic communication efforts, advertising produces both intended and unintended effects. However, there has been little systematic effort to synthesizing the unintended effects of advertising. This paper attempt to fill the gap in the literature. A thematic review was conducted to review the dimensions, types, and theories concerning the unintended effects of advertising. Variations of unintended effects in valence, levels of analysis, time lapse, content specificity, and audience types were discerned, on the basis of which a typology of 10 unintended effects was proposed, including confusion, reactance, and boomerang. The implications and directions for future research were discussed. It is hoped that the conceptual dimensions and types of unintended effects presented in this paper will serve as an evolving framework for endeavors to enhancing the theory and practice of advertising.