The cooperative output regulation problem of linear multi-agent systems using distributed observer approach has been solved under the assumption that each follower knows the system matrix of the leader system. To remove this assumption, in this paper, a distributed control scheme utilizing the adaptive distributed observer has been proposed, which consists of three steps. First, an adaptive distributed observer is designed to estimate both the system matrix and the state of the leader system. Second, an adaptive algorithm is developed to calculate the solutions of the regulator equations online. Third, both adaptive state feedback and adaptive measurement output feedback controllers are synthesized to solve the cooperative output regulation problem without the assumption that each follower knows the system matrix of the leader system. (C) 2016 Elsevier Ltd. All rights reserved.