[1] Born either in Tyresö, Sweden, or in Reval (modern Tallinn, Estonia), he was the son of Privy Councillor Gustaf Gabrielsson Oxenstierna and Barbro Axelsdotter Bielke.

He was sent as a legate to Denmark both in 1622 and 1625, and during the latter year he also visited Lübeck, Hamburg, Mecklenburg, Brandenburg, Pomerania, the Netherlands and England.

[1] After the death of Gustavus Adolphus in 1632, Oxenstierna travelled to Germany to meet his brother Axel.

[2] Gabriel Gustafsson Oxenstierna died in Von der Linderska Palace, Stockholm on 27 November 1640.

Because of his service and loyalty to his home country, his children and grandchildren were created counts, under the name Oxenstierna of Croneberg.