Manufacturers and platforms are increasingly engaged in rewarded cooperative advertising, wherein manufacturers include platform information in national ads to receive advertising rewards. This study explores manufacturers' advertising decisions, as well as platforms' motivations for sharing demand information and their choices regarding selling formats within this cooperative advertising framework. Our findings suggest that the platform shows a higher propensity to share information in the agency selling format compared to the reselling format. Moreover, increases in consumers’ preference for the platform and spill over effect of advertising can increase the platform's incentive to participate in rewarded cooperative advertising. Furthermore, the platform prefers reselling to agency selling when the commission rate is either extremely low or high. This study contributes to the literature by simultaneously analysing cooperative advertising, information sharing and selling formats in online retailing.