Participation in fantasy sports has become one of the most popular forms of interactive online entertainment, attracting more than 32 million players in North America. The purpose of this study was to examine the biasing effects of an advertisement promoting the popular online service. Using the illusion of control theory as a framework, a 2 × 2 between-subjects experiment (N = 156) was conducted to examine the effects of two marketer-controlled variables (i.e., customization level and expert information) on participants’ illusory judgments and their decisions to participate in the advertised service. The results showed that both manipulated features evoked biases in control perceptions. Furthermore, illusory control increases winning expectancy and increased winning expectancy leads to favorable attitude and decision toward the advertised product. Findings suggest that promotional information emphasizing control heuristics and expert knowledge can increase consumers’ beliefs that they can control their outcome, which subsequently influences their decision to participate.