Health communication campaigns, as an outcome of and an input into the social process, can create unintended as well as intended effects. The present paper represents an initial conceptual treatment of the unintended effects, the less studied of the two. It suggests that unintended effects can manifest in multiple dimensions, including those of time lapse, levels of analysis, audience types, content specificity, and valence. On these dimensions, a typology organizes available evidence to offer an outlook on 11 types of unintended effects, including obfuscation, dissonance, boomerang, epidemic of apprehension, desensitization, culpability, opportunity cost, social reproduction, social norming, enabling, and system activation. Implications for theory, research, and practice are discussed.