Abstract: Cycling is a promising zero-emission mode in the mobility domain globally. In Seoul however, only 2.58% of trips are by cycle in 2012 despite krw 74.6 billion investment from 2008 to 2012 by Seoul Metropolitan Government. The number of bicycle users increased rapidly over a decade but this has mainly been for leisure activities. This obviously reflects the limitations of the existing cycling system regarding travel times, distances and safety, as well as the dominant mobility culture. Considering that most travel in Seoul is for the purpose of commuting, it is highly desirable for a sustainable city to make cycling a key mode for commuting. This paper contributes to explore urban mobility transitions in an Asian megacity context. It analyzes the transition dynamics of the cycling system in Seoul from a socio-technical system viewpoint, drawing on the Multi-Level Perspective (MLP) and its phase model to capture the current limits and potentials of cycling as an important future commuting mode. The main drivers and barriers of a system transition are identified, considering niche, regime and landscape interactions. Based on the findings, the paper then suggests alternative approaches in policy and planning to foster the use of cycling as a commuting mode. In conclusion, electric bicycles and mobile phone applications are highlighted as important technology niches to overcome certain barriers. But also infrastructure improvements like the public transport transfer system and/or bicycle parking lots need to contribute to boost the modal share of cycling. Most importantly, however, various social and institutional aspects including user preferences, market mechanisms, policies, practices and cultures play a crucial role to promote and accelerate a transition in the cycling system.