An innovative negotiation methodology for strategic and tactical decision making is proposed for resolving conflicts in brownfield redevelopment. At the strategic level, the Graph Model for Conflict Resolution is systematically employed for determining a potential overall agreement, or set of resolutions, that is politically possible given the competing interests of the decision makers involved in a brownfield redevelopment project. At the tactical level, a possible strategic solution can be studied in depth using utility theory to determine trade-offs or concessions needed to reach a mutually acceptable detailed solution. Also, the proposed negotiation methodology can take into account the attitudes of negotiators and investigates the impact of the negotiators' attitudes on the outcome of negotiations at both levels of negotiation. The design of a negotiation decision support system is put forward to allow the proposed negotiation methodology to be conveniently applied to actual disputes.