This volume comprises carefully selected and reviewed outcomes of the 12thInternational Workshop on Automated Negotiations (ACAN) held in Macao, 2019, in conjunction with International Joint Conference on Artificial Intelligence (IJCAI) 2019. It focuses on human aspects of automated negotiation and the recent advances in negotiation frameworks and strategies. Written by leading academic and industrial researchers, it is a valuable resource for professionals and scholars working on complex automated negotiations.