Background Human brain organoids have attracted increasing attention for their potential to model human brain development and neurological disorders. However, concerns about their possible consciousness have generated ongoing ethical debate. In situations where scientific evidence remains uncertain but the possibility of serious moral harm cannot be excluded, the precautionary principle has been proposed as a framework for ethical governance. Methods This article critically examines the applicability of the precautionary principle to human brain organoid research through normative analysis. It clarifies core normative elements of precautionary principle and evaluates its relevance to emerging ethical challenges in brain organoid research. Results The analysis identifies several major governance challenges, including the epistemic limitations of similarity-based inference, tensions between evidentiary standards and precautionary obligations, and the risks of ethics dumping. These problems reveal broader governance gaps rather than theoretical disagreements, underscoring the need for institutional adaptation in advance of definitive scientific evidence. Conclusions The article argues that precautionary governance in human brain organoid research should avoid both excessive restriction and ethical complacency. It proposes strategies including dynamic and graded regulation, proportionality-based safeguards, and stronger international coordination. These approaches aim to balance ethical vigilance with responsible scientific innovation in a rapidly evolving field.