[4] Faced with an ideological choice between Zionism and Communism, he opted for the latter, and, in 1939, joined the then-illegal Romanian Communist Party, being introduced by a clandestine activist whom he knew by the pseudonym Kappa.

Later the Ion Antonescu régime interned him in a forced-labor camp, where, together with other persons of his age, he worked on construction teams until freed by the Soviet Red Army in 1944.

[5] Refusing promotion on the basis of political affiliation at a time when the Communist Party participated in Romania's governments, he became instead a welder in the large Bucharest factory owned by Nicolae Malaxa.

[4] Initially welcoming Soviet occupation, Moscovici grew increasingly disillusioned with communist politics, and noted the incidence of antisemitism among Red Army soldiers.

[4] Choosing clandestine immigration, he arrived in France a year later, having passed through Hungary and Austria, and having spent time in a refugee camp in Italy.

[3][5] At the time, Moscovici became close to Paris-based writers, including the Romanian-born Jewish Paul Celan and Isac Chiva [fr].

[3][7] In reference to himself, Celan, and Moscovici, Chiva later recalled: "For us, people on the Left, but who had fled communism, the first period in Paris, in a capital where the intellectual environments were developing under full-scale Stalinist enthusiasm, was very harsh.

He worked initially in the Social Psychology Laboratory, created on rue de la Sorbonne by Daniel Lagache.

[9] He served as a visiting professor at the New School in New York City, at the Rousseau Institute in Geneva, as well as at the Université catholique de Louvain and at the University of Cambridge.