After completing high school at Saint Sava College in 1903, he studied Philosophy and Law at the University of Bucharest, earning a J.D.

After auditing some penal law courses at Sorbonne University in Paris, he returned to Bucharest and registered in 1911 with the Ilfov County Bar as a defense lawyer.

[1][2] In 1923, Petrescu stood trial for alleged insults addressed to the Romanian Army; with the help of a defense team that included Dem I. Dobrescu, he was acquitted.

Petrescu was actively involved in the preparations for the August 1944 coup d'état organized by King Michael I, which led to the fall of Conducător Marshal Ion Antonescu.

Detained at Jilava, Sighet, and Râmnicu Sărat prisons, he was liberated after 7 years in December 1955, after the United Kingdom Labour Party had interceded with Nikita Khrushchev.