As sustainability challenges increasingly require societies to balance economic benefits with ecological balance, understanding how people evaluate resource allocation agreements has become an important research question. Perceptions of fairness play a central role in determining whether individuals support negotiated outcomes. Consequently, identifying the factors that shape fairness judgments can provide valuable insights into public acceptance of sustainability-related decisions in negotiations. The present study examined whether ecological sufficiency, equality principles, and evaluator role influence perceptions of fairness in sustainability-related negotiation outcomes.