Negotiations trigger anxiety. Across four studies, we demonstrate that anxiety is harmful to negotiator performance. In our experiments, we induced either anxiety or neutral feelings and studied behavior in negotiation and continuous shrinking-pie tasks. Compared to negotiators experiencing neutral feelings, negotiators who feel anxious expect lower outcomes, make lower first offers, respond more quickly to offers, exit bargaining situations earlier, and ultimately obtain worse outcomes. The relationship between anxiety and negotiator behavior is moderated by negotiator self-efficacy; high self-efficacy mitigates the harmful effects of anxiety.