The studies reported in this article examined the influence of context-induced and ad-induced affect on online (real time) and offline (memory-based) judgments in the context of disease (hepatitis B) prevention advertising among college students in Taiwan. An experiment with three between-subject factors the source of affect (context-induced versus ad-induced), the valence of the affect (positive, neutral, or negative), and the timing of evaluation (online versus offline) showed that both context-induced and ad-induced affect influenced online ad effectiveness but through different mechanisms. Context-induced affect influenced ad effectiveness through changes in processing strategies. Ad-induced affect influenced responses to the ad and the advocated health issue through either an affect as information mechanism or an affect priming mechanism, depending on the processing strategies triggered by context-induced affect. For offline judgments, ad-induced affect but not context-induced affect influenced ad and issue-related evaluations, because the former was more relevant to the advocated issue and thus more likely to be retrieved from memory when viewers evaluated the issue.