Zoos have tremendous potential and responsibility to conduct research, which is a key part of the European Association of Zoos and Aquariums’s (EAZA) Code of Ethics. Yet, the contributions of EAZA institutions to the peer-reviewed literature has never been quantified. By conducting an exhaustive Web of Science (WoS) database search, we quantified the peer-reviewed research contribution from 293 EAZA Members in the period 1998-2018. A total of 3345 peer-reviewed manuscripts were published in the 21-year period. The research output increased over time, with more than a threefold increase during the last decade. More than two thirds of all EAZA Member institutions published during the time period, but contributions were markedly skewed, with only seven institutions responsible for more than 100 publications each, thus contributing 37 % of the total output. The top three research areas were zoology, veterinary sciences, and environmental sciences and ecology, with the two former attributing to twice as many publications as the latter.