The ISEE international workshop on "Decadal challenges for the convincing climate projection and S2S scale prediction of Asian monsoon system" was held in ISEE, Nagoya University on 2–5 September, 2019. A total of 26 international researchers (including 1 remote attendee) participated in the workshop. We reviewed results from the past international Asian monsoon experiments under the GEWEX (The Global Energy and Water cycle Exchanges) and then discussed key issues in the hydroclimate science in Asian monsoon region to develop a science plan of the AsiaPEX (Asian Precipitation Experiment) project, which recently started as a prospective RHP (Regional Hydroclimatological Project) under the GEWEX. Based on this workshop, a review paper will be submitted to an international research journal.