This paper aims to explore the ASEM’s enlargement policy centered on the implication of 2010 enlargement with the special emphasis on the Russian accession. The enlargement in 2010 to include not only Australia and New Zealand but also Russia brings us to reconsider the bi-regional approach which upholds ASEM’s working process. The enlargement to Russia and less so for Australia and New Zealand, is expected to bring challenges to the region-based coordination process of ASEM especially considering the fact that Russia has an indefinite identity between Asia and Europe. Then, would this enlargement affecting the region-to-region approach, the modus operandi of ASEM, shifts ASEM’s bi-regional inter-regionalist nature to a trans-regional inter-regionalist one? This paper argues that the 2010 enlargement was not aimed at changing ASEM’s working process nor its bi-regional inter-regionalist format. In other words, ASEM had no intention of fundamentally changing its working process to trans-regionalism, but was mindful of the benefits from accepting Russia's membership. ASEM’s seeming inclination to trans-regional inter-regionalist format can be interpreted as the means forced by circumstances to include Russia and further to include other countries in Eurasia to ASEM. The accession of Russia, the representative country of Eurasia, thus can be regarded most persuasively as the principal rationales of ASEM: to counterbalance the US' hegemonic stance, as one of the primary rationales of ASEM suggests, and also to counterweight against unrivaled China in ASEM which is becoming the potential threat to ASEM's existence. This paper also observes Korea's stance on the Russian accession to ASEM including the consecutive enlargement of ASEM from 2008. In particular, it analyzes the outcomes of Russia's accession such as stabilized energy supply by the Russia-North Korea-South Korea natural gas pipeline and the easing of tension on the Korean Peninsula together with the changing perspective of ASEM through its enlargements.