Online sports betting has been increasingly used thanks to online betting sites’ excessive marketing and advertising. Two between-subjects experimental studies tested how the presence of celebrities or betting inducements on social media advertisements influences consumer attitudes and behaviors. Results show that celebrity endorsements and inducements independently affect attitudes and behaviors without significant interaction effects. Exposure to advertisements from a celebrity rather than a brand increases positive brand attitudes and advertisement sharing intentions but not betting site use intentions. The presence of inducements in advertisements appears to increase brand attitudes, advertisement sharing intentions, and betting intentions. Brand–celebrity congruence leads to higher brand attitudes and betting intentions, but not advertisement sharing intentions. The impact of brand–celebrity congruence on attitudes and behavioral intentions was moderated by favorable attitudes toward the celebrity, indicating that favorable celebrity images could be more influential when online sports betting brands collaborate with celebrities exhibiting low brand–celebrity congruence. Theoretical and practical implications for online sports betting advertising and its impact are discussed.