He was born in Kalamata and he was the son of the banker Ioannis Kostopoulos.
He dealt with the banking industry, in which the family already had developed significant activity.
He was a member (1937-1951) and President (1951-1953) of the board of the Commercial Credit Bank.
In the elections of 1946, he was reelected for the Liberal Party, gathering 2.491 votes.
Having already come into conflict with Andreas Papandreou, during the Apostasia of 1965, he was among the first members of the Centre Union to leave the party and became Minister of National Defence in the Georgios Athanasiadis-Novas government.