ABSTRACT The media landscape changes have resulted in significantly more people viewing content in shorter and skippable formats. There is limited evidence about the impact of these formats on anti-tobacco campaign effectiveness. This study examined the effect of anti-tobacco ad length and skippability on perceived message effectiveness (PME) and emotional responsiveness among people who smoke. Initially, 805 people who smoke were randomized to a message type (anti-tobacco vs. control) × message length (15 vs. 30 seconds) condition. A week later, participants saw the same message, but were randomized to a skippable or non-skippable version. Following ad exposure, outcomes were measured and examined in mixed-effects linear regression models. We found that at initial exposure, participants in the 30-second anti-tobacco condition reported significantly higher scores on personal relevance (75% cf. 68%), motivation to act (61% cf. 52%), action-oriented negative emotion (62% cf. 53%) and positive emotion (37% cf. 28%) relative to participants in the 15-second anti-tobacco condition. At repeated exposure, there was no effect of ad skippability on PME or emotional responsiveness regardless of message type condition. However, participants in the 30-second anti-tobacco condition reported significantly higher scores on action-oriented negative emotion (60% cf. 50%) and inaction-oriented negative emotion (54% cf. 46%) relative to participants in the 15-second anti-tobacco condition. Our findings suggest that initial exposure to non-skippable and longer novel anti-tobacco messages can lead to stronger personal relevance, motivation to act and emotional arousal, and ongoing negative emotional arousal, which may attenuate the negative effects of allowing individuals to skip later.