The Asian Development Bank (adb) has made increasingly important contributions to Asia's (and particularly East Asia's) regionalism over recent years, and especially since Haruhiko Kuroda became the Bank's president in February 2005. This paper argues that the adb's role here has become more significant because of the strong 'developmental' characteristics of East Asia's new regionalism. This is not least because, as a regional development bank, the adb has a predilection for linking development, regionalism and capacity-building together when promoting regional co-operation and integration (rci) in Asia. We may refer to this as 'developmental regionalism', where rci activities are particularly orientated to enhancing the economic capacity and prospects of less developed countries with the view of strengthening their integration into the regional economy, and thereby bringing greater coherence to regional community building overall. This analysis is partly based on field research undertaken by the author involving a series of research interviews conducted amongst adb officials and with outside analysts of the organisation. It first examines the evolution of the Bank's stance and policies on rci, and the impact made by President Kuroda and the newly formed Office of Regional Integration (orei) in this regard. The main developments of East Asia's new regionalism are then outlined from finance and trade perspectives. Thereafter, an evaluation is made of the adb's contributions toward the emerging developmental regionalism in East Asia.