Tōgō returned to Japan in 1933 to assume the post of director of the Bureau of North American affairs, but was in a severe automobile accident which left him hospitalized for over a month.

During this time, he negotiated a peace settlement following the Battles of Khalkhin Gol between Japan and the Soviet Union, and successfully concluded the Soviet–Japanese Neutrality Pact in April 1941.

Together with Mamoru Shigemitsu he made unsuccessful last-ditch efforts to arrange for direct face-to-face negotiations between Prime Minister Fumimaro Konoe and US President Franklin Roosevelt in an attempt to stave off armed conflict.

Once the Empire had decided on attacking, Tōgō signed the declaration of war, as he disliked pressing the responsibility of the failure of diplomacy on others.

As part of a more reconciliatory policy towards the western powers, Tōgō announced on 21 January 1942 that the Japanese government would uphold the Geneva Convention, even though it did not sign it.

Upon the formation of the government of Admiral Kantarō Suzuki in April 1945, Tōgō was asked to return to his former position as Minister of Foreign Affairs.

In that position, he was one of the chief proponents for acceptance of the Potsdam Declaration which, he felt, contained the best conditions for peace Japan could hope to receive.

However, the Supreme Commander of the Allied Powers soon ordered his arrest on war-crime charges, along with all former members of the Imperial Japanese government; he was held at Sugamo Prison.

In 1922, despite the strenuous objections of Tōgō's family, he married Carla Victoria Editha Albertina Anna de Lalande (nee Giesecke 1887-1967), the widow of noted German architect George de Lalande (1872-1914) who designed numerous administrative buildings in Japan and its empire, including the Japanese General Government Building in Seoul.