Abstract: As the two most significant Asian powers, competition in infrastructure sectors in Asia between China and Japan is inevitable. Japan is a long-established developer of regional infrastructure in Southeast Asia, while China’s interest in financing and building infrastructures there is relatively recent. After China proposed the Belt and Road Initiative (BRI) and the Asian Infrastructure Investment Bank (AIIB), Japan stepped up its efforts, determined to expand its already well-established influence. This competition has had positive as well as negative consequences for Southeast Asia and regional financial architecture. This article attempts to use Sino–Japanese competition for infrastructure financing and high-speed railway contracts as a case in point to explore in what ways and trajectory these two countries’ competition for infrastructure investment is going on, and what impacts it will create on the region. Full text available here.