AbstractAimsTo test whether showing spectators counter‐advertisements exposing alcohol harms alone, or exposing alcohol harms and alcohol sponsorship, before watching an alcohol‐sponsored sporting event promotes less favourable post‐event attitudes and intentions towards alcohol sponsor brands and alcohol in general.DesignOn‐line between‐subjects experiment.SettingAustralia.ParticipantsA sample of Australian adults aged 18–49 years who planned to watch an alcohol‐sponsored National Rugby League (NRL) State of Origin series game was recruited through an online panel.InterventionsParticipants were randomly assigned to one of three counter‐advertising conditions: control (neutral advertisement); counter‐advertisement exposing alcohol harms; and counter‐advertisement exposing alcohol sponsorship and harms, to view at least four times during the week before watching the alcohol‐sponsored sporting event.MeasurementsParticipants (n = 1932) completed a pre‐test questionnaire a week before the sporting event. Within 4 days of watching the sporting event, participants completed post‐test measures assessing sponsor brand awareness, attitudes and preferences towards the brand, as well as knowledge, attitudes and intentions for alcohol in general (n = 1075).FindingsCompared with the control advertisement, the counter‐advertisement exposing alcohol sponsorship and harms promoted higher (6–13%) awareness of sponsor brands, less favourable attitudes towards sponsor brands and drinking beer, lower purchase intentions for sponsor brands (Cohen's d = 0.15, 0.31, 0.27, respectively) and perceived less image‐based similarity and fit between the sporting event and sponsor brands (Cohen's d = 0.20 and 0.56). Both counter‐advertisements promoted lower perceptions of the appropriateness of consuming alcohol while watching sport (Cohen's d = 0.22 and 0.34), higher awareness of alcohol harms (6–34%) and higher intentions (8–13%) to reduce alcohol consumption than the control advertisement.ConclusionsAt alcohol‐sponsored sporting events, counter‐advertisements addressing alcohol harms may promote knowledge of harms and intentions to drink less. Counter‐advertisements that additionally expose and critique alcohol sponsorship may detract from perceptions of sponsor brand image and intentions to purchase the sponsor's products.