A novel Scenario-Based Dynamic Negotiation approach is proposed for the coordination of decentralized Supply Chains under uncertainty. The relation between the involved organizations (client, provider and third parties) and their respective conflicting objectives is captured through a non-zero-sum and non-symmetric roles SBDN negotiation. The client (leader) designs coordination agreements considering the uncertain reaction of the provider (follower) resulting from the uncertain nature of the third parties, which is modeled as a probability of acceptance. Different negotiation scenarios are studied: i) Cooperative, and ii) Non-Cooperative and iii) Standalone cases. The use of the resulting models is illustrated through a case study with different vendors around a "leader" (client) in a decentralized scenario. Although the usual cooperation hypothesis will allow higher overall profit expectations, using the proposed approach it is possible to identify non-Cooperative scenarios with high individual profit expectations which are more likely to be accepted by all partners.