Domestic support for a nuclear South Korea is increasingly noticeable—with envisioned pathways including the return of US tactical nuclear weapons, a NATO-style nuclear sharing agreement and an indigenous nuclear programme. Existing accounts largely frame the issue in terms of Washington-Seoul alliance management and a single defining North Korean threat, focusing on questions of ‘why’ South Korea should/should not pursue nuclear options. In this article, I instead reframe the debate as a broader regional security issue, investigating how South Korea’s Indo-Pacific neighbours might view and respond to the activation of these nuclear pathways. Drawing on interviews and exchanges with nuclear and regional security experts, this article provides a preliminary and tentative sketch of the perspectives of foreign policy elites in six Indo-Pacific states: the United States, China, Japan, India, Indonesia and Australia; and also Taiwan. I conclude the article by offering further policy-relevant insights into how regional states can act, both individually and collectively, to lessen the prospects of a nuclear South Korea.