Wolfhart Pannenberg would have been 90 years old in 2018. This article is a tribute to his excellent contribution to the ecumenical debate on church unity and the importance to reach an agreement on the doctrine of justification. The first step is to explain Pannenberg's Lutheran understanding of church unity. Secondly, Pannenberg's contribution to mobilise understanding for the ecumenical efforts in coming to an agreement on the doctrine of justification is discussed. His efforts in convincing theologians that one cannot work towards church unity while churches continue to condemn one another for having different views on doctrinal matters, receive special attention. Pannenberg's effort to convince his colleagues that one should approach these sensitive ecumenical matters from the perspective of present-day historical-critical thinking is also mentioned. The article concludes with a judgement on his approach and his success in these matters.