By the end of 1946, the monarchy was abolished and the People's Republic of Bulgaria was declared with Georgi Dimitrov of the Bulgarian Communist Party (BCP) as Prime Minister. The Party gradually gained absolute control over the decades in politics, economics and culture, and thousands of private enterprises, estates and industries were taken into the state holdings. In 1948-49, the Party severely restricted or forbid all religious activities and organizations, and under Stalin-appointed Vulko ("Little Stalin") Chervenkov who was Dimitrov's successor, over 90 000 dissidents were obliterated via expulsions, arrests and killings in an anti-Titoist purge in 1948-49.

The 1950's brought slightly more relaxed politics, mostly due to Stalin's death in 1953 and Chervenkov's loss in Party elections to Todor Zhivkov the next year. During Zhivkov's era, Bulgaria towed the Communist line to the letter, often called (even by Bulgarians) the 13th Soviet Republic. In return for Party loyalty came a secure job, enough food, education, health care and the reputation of one of the most prosperous Eastern European countries at the time. Those who didn't adhere to the strict Soviet policies were marginalized and denied access to educational, personal and job opportunities, so most had little choice but to accept what the Party had to offer.

Most feared was the DS (Dirhavna Sigurnost), the State Security force, whose name is connected with the poison-tipped umbrella killing of dissident writer Georgi Markov in the London Underground in 1978, as well as a plot to kill the Pope in 1981, although in 2002 the Pope said he did not believe that Bulgaria had been behind the assassination attempt.

Under Zhivkov, Bulgarian Socialist nationalism grew, with many monuments erected in memory of heroes of Bulgarian history who had helped to bring the country to its Communist success, and therefore had not died in vain. Minority groups such as the Roma (Gypsy) and Turkish populations were not so glorified, and beginning in the 1950's were systematically marginalized, denied access to basic services and forced to renounce their own names in favour of Bulgarian ones. Those who refused to do so were further marginalized or even sent to concentration camps, and in 1984 a violent spark was ignited over the issue. Amid growing concern over human rights issues from Western and even other Communist countries, five years later in 1989, thousands of ethnic Turkish Bulgarians left the country rather than be assimilated into Zhivkov's increasingly disliked nationalist strategy.