This study examines when and why threats of economic sanctions lead to successful extraction of policy concessions. Scholars identified three hypotheses that explain success of sanction threats: the coercive, the informational and the public commitment hypothesis. The underpinning mechanisms for the hypotheses are, respectively, the economic cost of sanctions, uncertainty about the resolve of the sender and domestic audience cost for issuing empty threats. In this study, we offer an empirical test of the three hypotheses on threats effectiveness. In addition, we assess how variation in the three mechanisms affects effectiveness of threats relative to imposed sanctions. Our results show that effectiveness of threats strongly increases in economic cost to the target; however, threats become increasingly effective relative to imposed sanctions for lower uncertainty and higher domestic audience cost.