Born in Bârlad, he attended the city's Gheorghe Roșca High School.
Hamangiu became a circuit judge in Bucharest in early 1894, and a substitute prosecutor at the Vâlcea County tribunal later that year.
That autumn, he became an adviser at the High Court of Cassation and Justice, a post he retained until his death.
[2] In 1930, he was elected an honorary member of the Romanian Academy, an institution to which he made significant donations.
In April 1931, he was named Justice Minister in the technocratic cabinet of Nicolae Iorga.