China and the United States have developed a complex relationship. Facing common threats such as missile proliferation and regional instability, they tend to collaborate for mutual benefit. However, the two countries have hedged against each other for their respective national interests, often acting so as to reinforce each other’s negative security perceptions. Their security dynamism in missile defense and antisatellite (ASAT) operations has furthered their mutual distrust. This article addresses their security dilemmas by suggesting that China and the United States take a more trusting view of each other’s missile defense program, whether at the research and development stage or at deployment. They must develop such systems in an approach of mutual reassurance, allowing a degree of reciprocal vulnerability in order to avoid an arms race. An interim partial space security arrangement is also proposed here, namely, a limited ASAT ban for satellite security in outer space, to soothe respective security concerns and meet each country’s present need.