Constantinos Tsatsos was born in Athens in 1899 and lived there until his death in 1987. He was married to Ioanna Seferiadou and had two daughters. He studied law at Athens University.

Along with his studies he also took an interest in the works of classical Greek and Latin writers as well as contemporary Greek literature and poetry. He published two volumes of poetry and plays under the pseudonym Yves Delfos.

From the end of the First World War until 1920 he served in the Greek diplomatic delegation to Paris. In this capacity he took part in the negotiations leading to the signing of the Treaty of Sevres.

After completing his postgraduate studies in Philosophy and the Philosophy of Law in Heidelberg, he returned to Athens. He was awarded a Ph.D in Law in 1929, became an Associate Professor in 1930 and a Professor in Athens University Law School in 1932 teaching Introduction to the Science of Law and Philosophy of Law. During the Metaxas dictatorship he was arrested and banished to the island of Skyros. In 1941 he was dismissed from the university and in 1944 fled to the Middle East.

After the liberation he returned to his post at the university and in 1945 served as Minister of the Interior in the Voulgari Government and as Press and Information Minister in the Kanellopoulos Government. In 1946 he resigned from the university and stood for election with the Liberal Party. He served as Minister of Education in the Sofouli Government (1949) and as Deputy Minister of Coordination in the S. Venizelos Government (1951).

In 1956 he joined the newly-founded National Radical Union (ERE) Party with which he was successful in every election. He served as Minister to the Prime Minister's Office and Minister of Social Welfare in the Karamanlis Government (1961, 1963) and as Minister of Justice under the Kanellopoulos Government (1967).

After the restoration of democracy in 1974, he took over the Ministry of Culture in the National Unity Government. In the parliamentary elections of 1974 he became Member of Parliament for the State with the New Democracy Party.

On 20 June 1975 Constantinos Tsatsos was elected President of the Republic by parliament, receiving 210 votes from the 295 Members of Parliament present. He served as President until May 1980.

Constantinos Tsatsos published a large number of scientific studies, legal and philosophical books, as well as literary works. In 1961 he was elected to the Athens Academy of which he was later vice-president and then president. In 1979 he was elected to the French Academy of Ethical and Political Sciences as a foreign member and made an honorary professor of the Sorbonne. He was also elected as a foreign member to the Rumanian and Moroccan Academies in 1980 and a member of the European Academy of Sciences, Arts and Letters in 1981. In 1980 he was awarded the important European Coudenhove-Kalergi prize.