Integrating recent work on emotional communication with social science theories on unpredictability, we investigated whether communicating emotional inconsistency and unpredictability would affect recipients' concession-making in negotiation. We hypothesized that emotional inconsistency and unpredictability would increase recipients' concessions by making recipients feel less control over the outcome. In Experiment 1, dyads negotiated face-to-face after one negotiator within each dyad expressed either anger or emotional inconsistency by alternating between anger and happiness. In Experiment 2, participants received angry and/or happy messages from a simulated negotiation opponent. In Experiment 3, participants read a scenario about a negotiator who expressed either anger or emotional inconsistency by alternating between anger and disappointment. In all three experiments, emotional inconsistency induced recipients to make greater concessions compared to expressing a consistent emotion. Further, in all three experiments, the effect of emotional inconsistency was mediated by recipients' feeling less control. These findings qualify previous research on anger in negotiation and demonstrate the importance of feelings of control for negotiation outcomes.