Conspiracy theories are prevalent in present-day China regarding the United States. Many people are highly vigilant about US intentions and behaviours, and perceive that the United States is shrewdly and intentionally making every effort to discredit, weaken and contain China, so that its own primacy and dominance are maintained. This chapter discusses psychological, socio-political and international factors in explaining the phenomenon. First, people tend to employ simple explanations rather than sophisticated, institutional analysis when they encounter sudden, mysterious, complicated events. Second, there is the domestic socio-political context including decreasing level of social trust, elite/interest group manipulations, rising nationalism, and the changing political atmosphere. Third, the state of bilateral US–China relations is also identified as a factor accounting for the popularity of conspiracy theories. The exaggeration of the influence and effects of conspiracy theories may lead to serious negative consequences in China and in its relations with the United States. It reinforces the enemy image, alienates the American and Chinese people, and shapes a detrimental atmosphere for governmental relations.