For decades prior to the Presidency of Woodrow Wilson (1913-1921), secrecy simply was not integral to U.S. international diplomacy. Yet Wilson’s emphasis on maintaining secrecy in his negotiations led to a newly incipient culture of secrecy in American foreign affairs. Bridging previously separate subdisciplines, international and cryptologic history, this article examines changes in U.S. diplomatic code and cipher practice, which reflect a broader evolution of official attitudes towards diplomatic secrecy in this period. It provides a novel prism through which to view the introduction of greater secrecy amid a tradition of transparency in American foreign affairs.