Prior studies on customer–supplier negotiations (Drake & Haka, 2008; Van den Abbeele, Roodhooft, & Warlop, 2009) find that negotiators who have access to relevant activitybased cost information are not always able to use this information to improve joint outcomes Our study extends this literature by examining how the type of accountability (process and outcome accountability) influences the extent to which negotiators can obtain lower join costs. We hypothesize and test a model that predicts that the type of accountability affects negotiated outcomes through its effect on negotiators’ fixed-pie bias revisions and the negotiation tactics they employ during customer-supplier negotiations Results from an experiment show that negotiators held accountable for their negotiation processes are better able to reduce their fixed-pie biases and achieve lower joint costs compared to those who are held accountable for their negotiation outcomes. Using rich data based on taped negotiations, we demonstrate that the effect of accountability on joint costs is indirect through its effect on negotiators’ choice of negotiation tactics and the extent to which negotiators can reduce their fixed-pie biases