Competition lies at the heart of our economic, social, and political lives. Studies show that competitions motivate higher performance, but they can also have a dark side, by which competitors engage in deceptive, dishonest, and sabotaging conduct. In the paper’s primary study, we compare competitive behavior at 4 levels of competition intensity. As expected, we find that intensifying the competition has a general effect of increasing both the effort invested in the task and the tendency to sabotage the counterpart. We were particularly interested in whether participants would engage in sabotaging behavior at the lower boundary of competitive intensity that was devoid of any incentive to outperform the counterpart and also precluded any prospect for social comparison or social facilitation. In this condition, participants were matched with another person performing the same task, knowing that their relative performance will have no effect on payoffs and will not even be shared with each other. We found that, by itself, this illusory competition did not motivate higher performance, but when given the option to engage in (costly) sabotage, almost one quarter of participants chose to sabotage their illusory counterpart. The paper’s secondary study replicated this finding using a stimulus that included a comprehension test. These findings reveal competitive behavior under circumstances that, to the best of our knowledge, fall short of previously investigated types of competition. Theoretical explanations and normative implications are discussed.