In Japan, environmental education partnerships among citizens, businesses and local government increased since new legislation was introduced in 2003, but there was little evidence of cross-sector collaboration until recently. Nagoya Open University of the Environment is a highly innovative, multi-sectoral citizen learning system founded in 2005 with the objective of positioning Nagoya City as a global centre of excellence in sustainability. This article discusses the university's background and structure and its achievements and outstanding issues, including (1) progress in cross-sector partnerships, (2) the voluntary participation of more than 20,000 citizens, (3) the implementation of classroom-based learning, surveys, field studies and social experiments, (4) the need for expansion and a stronger financial base, and (5) the importance of promoting ESD under the umbrella of Regional Centres of Expertise (RCE), Chubu. (Contains 2 notes, 1 table, and 9 figures.)