Vietnam has tried to maintain a delicate balance between the United States and China by pursuing a hedging strategy. In a shifting strategic environment marked by structural uncertainty caused by the rise of China, weaker Southeast Asian states like Vietnam are projecting a non-alignment posture. However, this rational behavior is not the product of systemic factors alone but also certain domestic political dynamics. We argue that regime legitimation – how the Vietnam Communist Party seeks to generate and sustain internal and external legitimacy – weighs heavily on Vietnam’s strategy toward US–China competition. In particular, three legitimation strategies employed by the Vietnam Communist Party – performance-based legitimation, nationalism-based legitimation vis-à-vis China, and defensive legitimation vis-à-vis “hostile forces” – produce dynamics that ensure Hanoi does not get inadvertently pulled into the orbit of either Beijing or Washington. Theoretically, this article contributes to the literature on domestic determinants of foreign policy with a focus on regime legitimation. Empirically, we seek to supplement the discussion on the salience and relevance of domestic politics in informing Southeast Asian states’ strategic calculation amid great-power competition.