We discuss self-serving uses of equity in international climate negotiations. Using unique data from a world-wide survey of agents involved in international climate policy, we show that the perceived support of different equity rules by countries can be explained by the ranking of their economic costs. Despite being self-serving, equity arguments may be perceived as being used for different reasons, e.g. out of fairness considerations or to facilitate of negotiations. Consistent with experimental and behavioral studies, we find empirical evidence for self-serving biases: individuals are more likely to state reasons with positive attributes if they evaluate countries that support the individual’s personally preferred equity rule. Negotiators perceive countries’ use of equity as less influenced by pressure from interest groups.