["International Journal of Consumer Studies, Volume 50, Issue 3, April 2026. ", "\nABSTRACT\nThis study investigates the negative impacts of complex marketing initiatives during online sales events, also known as online shopping carnivals (OSCs). We focus on consumer confusion and how it affects consumer behavior. OSCs, such as China's Double Eleven, can boost sales and consumer engagement, but they also present challenges. Using data from a scenario‐based survey, this research examines how the complexity of marketing initiatives run by platforms and merchants increases consumer confusion, reduces purchase intention, leads to negative word‐of‐mouth, and decreases perceived enjoyment. The results suggest that although marketing initiatives are designed to enhance consumer engagement, their complexity can result in undesirable outcomes. This highlights the dark side of OSCs. Our findings have valuable implications for e‐commerce practitioners seeking to optimize their marketing strategies and ensure satisfied customers during OSCs. In particular, platforms and merchants may benefit from simplifying marketing terms and collaborating to avoid conflicting offers, thereby reducing consumers' cognitive overload.\n"]