In 1935, at the request of President Atatürk, Fuat Köprülü joined the single party regime in the Turkish Parliament as a Kars deputy, and was elected again in 1939 and 1943. In 1945, as calls to establish a multiparty democracy increased after World War II, Fuat Köprülü joined the opposition and was dismissed from the ruling party along with Adnan Menderes and Refik Koraltan. In 1946, Menderes, Koraltan and Köprülü, together with Celal Bayar, formed the Democratic Party. Fuat Köprülü became the Minister of Foreign Affairs when the Democratic Party came to power in the 1950 elections, and he served in this post until 1955. In 1953, an agreement was reached between Yugoslav President Tito and Fuat Köprülü that promoted the emigration of Albanians from Yugoslavia to Anatolia. Concerning Cyprus, he had a tolerant view of the dispute and supported the line of the Turkish government, that the status quo of a British government on the island was favorable. Fuat Köprülü also briefly served as Deputy Prime Minister in 1955. On September 6, 1957, Fuat Köprülü resigned from the Democratic Party after disagreeing with the authoritarian tendencies displayed by the party leadership; same year he joined Liberty Party. Following the coup d'état in 1960 he was tried at the Yassıada trials but found not guilty.