This chapter starts by outlining how Knowledge Validation is understood in the Knowledge Management (KM) literature. Through the operationalization of stage two of the KM model applied in this book, the chapter then goes on to investigate how Knowledge Validation has taken expression in the UN First Committee cyber negotiations. In other words, this chapter examines how input provided to these negotiations has gained acceptance or come to be considered legitimate amongst negotiating diplomats. Considering this, the chapter finds that while there is no formal mechanism in place for validating contributed input, Knowledge Validation does, however, occur through three means. These means include validation by association or by proxy, validation by personal expertise, as well as validation through political acceptance.