During the American Civil War, Yancey was appointed by Confederate President Jefferson Davis to head a diplomatic delegation to Europe in the attempt to secure formal recognition of Southern independence. In these efforts, Yancey was unsuccessful and frustrated. Upon his return to America in 1862, Yancey was elected to the Confederate States Senate, where he was a frequent critic of the Davis Administration. Suffering from ill health for much of his life, Yancey died during the Civil War, in July 1863 at the age of 48.