As of August 2017, hundreds of thousands of Rohingyas were forced to flee Myanmar, where they were the victims of violence, and take refuge in Bangladesh. In October 2017, the DEC launched an appeal for funds to meet the needs of these refugees and the host population in the region of Cox’s Bazar. The members of the DEC, and the humanitarian system as a whole, had to deal with numerous challenges during this unprecedented crisis. This report describes the main lessons learned.