Recent developments in applying reinforcement learning to cooperative environments, like negotiation, have brought forward an important question: how well can a negotiating agent be trained through self-play? Previous research has seen successful application of self-play to other settings, like the games of chess and Go. This paper explores the usage of self-play within the training of a negotiating agent and determines if it is possible to successfully train an agent purely through self-play. The results of the experimentation show that a training stage using self-play can match or even exceed an approach using a set of training opponents. By using multiple self-play opponents, the average utility can be further improved by introducing more variance during training. In addition, using a combination of both self-play and training opponents leads to a hybrid approach that performs better than either of the two techniques separately.