Ushiba's foreign service career faltered badly in the post-war period due to his close association with General Ōshima and his service in Germany. Although he was never formally purged from the service, he quit. He served as Ōshima's defense counsel during the Tokyo War Crimes Trials, and then went into private business. He and some friends attempted to import Malaysian iron ore, but their business quickly failed. He was rehabilitated and brought back into the foreign service by Shigeru Yoshida, Prime Minister of Japan, who knew him when Yoshida was Japan's ambassador to the United Kingdom just before the war.