Ewert was born in Athens on May 12, 1939, the son of Angelos Ewert who, later, became Chief of Police. He studied economics at the University of Athens and joined EREN (the youth organisation of the National Radical Union, the conservative party in power at the time) in 1957 becoming its leader in 1963.
During the time of the military dictatorship (1967 - 1974), his activities were curtailed and he was forbidden to leave the country. After the restoration of democracy in July of 1974, Ewert joined New Democracy, the successor of the National Radical Union, and was elected under its banner to the Hellenic Parliament. He was continually re-elected until his retirement from politics in 2009. In October of 1986, he was elected Mayor of Athens resigning his seat in Parliament to assume office on December 20. He resigned as Mayor of Athens on May 3, 1989 in order to run for MP in the general election of June 1989.
He served as Minister for Industry and Energy, 28-11-1977 to 10-05-1980; Minister for Finance, 10-05-1980 to 17-09-1981 and 17-09-1981 to 21-10-1981; Minister for Health, Welfare and Social Security, 02-07-1989 to 12-10-1989; and Minister for the Presidency, 11-04-1990 to 07-08-1991 and 07-08-1991 to 26-10-1991.