His father, Gheorghe Niculescu-Mizil, was reportedly a shop assistant, trade unionist, and self-taught poet, known for contributing to PSDR and PS gazettes, from România Muncitoare to Socialismul, and eventually joining the outlawed Communist Party (PCdR or PCR).

[2] According to their official biographers, Gheorghe and his wife Eufrosina Cotor Niculescu-Mizil ran a PCdR meeting house during World War II, as opponents of the Ion Antonescu dictatorship.

[3] Paul Niculescu-Mizil was a student at the military officers' school in Ploiești during the war, and right after King Michael's Coup, his unit was sent to help retake Northern Transylvania.

[4] He headed the PMR's propaganda and agitation section between 1956 and 1965,[5] where, as Leonte Răutu's deputy, he was one of the few persons with access to the latter's house, and backed his strident attacks on Romanian culture.

There, he made a striking gesture, leaving the room in protest at Soviet attacks on Romania's position of defending the principle of equality and independence within the global communist movement, in particular Czechoslovakia's right to carry out the reforms of the Prague Spring.

From 1965 to 1969 he was on the leadership of the Romanian Society for Friendship with the Soviet Union and of the National Committee for Defending Peace, and served as Romania's permanent representative to the Comecon from 1979.

[1] As Ceaușescu's rule, the economic, political and cultural excesses of which he openly criticized on several occasions,[7][8] became more personal and his policies less predictable, Niculescu-Mizil gradually lost influence.

[5][11] Accounts differ on what in fact occurred: one suggests he had no real power and could not influence events either way,[7] one claims he opposed opening fire on demonstrators in Timișoara,[8] while another states he backed Ceaușescu's decision to use force.

Alongside other top party activists, including Manea Mănescu, Ștefan Andrei, and Dumitru Popescu, he promoted the idea of a break between the "Comintern" phase of the 1950s and the later national communism, allegedly patriotic and enlightened.

[5] Although he sought to avoid what Tismăneanu calls the "police-state brutalities and asphyxiating dogmatism of a sclerotic ideology", his defense of the system ignored its classically Stalinist features such as censorship, the Securitate secret police, and hyper-bureaucratic planning.