BACKGROUND: Tobacco counter-advertising is effective at promoting smoking cessation. Few studies have evaluated the impact of alcohol warning advertising on alcohol consumption and possible mechanisms of effect. This pilot study aimed to assess whether alcohol warning advertising is effective in reducing urges to drink alcohol, if emotional responses to advertising explain any such effect or perceived effectiveness, and whether effects differ among heavier drinkers. METHODS: One hundred fifty-two young adult (aged 18-25) alcohol users completed an online experiment in which they were randomly assigned to view one of three sets of six advertisements: (i) alcohol warning; (ii) alcohol promoting; or (iii) advertisements for non-alcohol products. Urges to drink alcohol were self-reported post-exposure. Affective responses (pleasure and arousal) to each advertisement and perceived effectiveness of each advertisement were recorded. Typical level of alcohol consumption was measured as a potential effect modifier. RESULTS: Participants exposed to alcohol warning advertisements reported significantly lower urges to drink alcohol than those who viewed either alcohol promoting or non-alcohol advertisements. This effect was fully mediated by negative affective responses (displeasure) to the alcohol warning advertisements. Perceived effectiveness of alcohol warning advertisements was associated with high arousal responses. Impact of the advertisements was unaffected by typical level of alcohol consumption, although the study was not powered to detect anything other than large effects. CONCLUSIONS: In line with findings from the tobacco literature, alcohol warning advertisements that elicit negative affect reduce urges to drink alcohol. Their impact upon actual consumption awaits investigation.