Although Dimitrov had been in exile, mostly in the Soviet Union, since 1923, he was far from being a Soviet puppet. He had shown great courage in Nazi Germany during the Reichstag Fire trial of 1933, and had later headed the Comintern during the period of the Popular Front. He was also close to the Yugoslav Communist leader Tito, and believed that Yugoslavia and Bulgaria, as closely related South Slav peoples, should form a federation. This idea was not favoured by Stalin, and there have long been suspicions that Dimitrov's sudden death in July 1949 was not accidental, although this has never been proved. It coincided with Stalin's expulsion of Tito from the Cominform, and was followed by a "Titoist" witchhunt in Bulgaria. This culminated in the show trial and execution of the Deputy Prime Minister, Traicho Kostov. The elderly Kolarov died in 1950, and power then passed to an extreme Stalinist, Vulko Chervenkov.

Bulgaria's Stalinist phase lasted less than five years. Agriculture was collectivised and peasant rebellions crushed. Labor camps were set up and at the height of the repression housed about 100,000 people. The Orthodox Patriarch was confined to a monastery and the Church placed under state control. In 1950 diplomatic relations with the U.S. were broken off. The Turkish minority was persecuted, and border disputes with Greece and Yugoslavia revived. The country lived in a state of fear and isolation. But Chervenkov's support base even in the Communist Party was too narrow for him to survive long once his patron, Stalin, was gone. Stalin died in March 1953, and in March 1954 Chervenkov was deposed as Party Secretary with the approval of the new leadership in Moscow and replaced by Todor Zhivkov. Chervenkov stayed on as Prime Minister until April 1956, when he was finally dismissed and replaced by Anton Yugov.

Zhivkov ran Bulgaria for the next thirty years, completely loyal to the Soviets but pursuing a more moderate policy at home. Relations were restored with Yugoslavia and Greece, the labour camps were closed, the trials and executions of Kostov and other "Titoites" (though not of Petkov and other non-Communist victims of the 1947 purges) were officially regretted. Some limited freedom of expression was restored and persecution of the Church was ended. The upheavals in Poland and Hungary in 1956 were not emulated in Bulgaria, but the Party placed firm limits to intellectual and literary freedom to prevent any such outbreaks. Economic conditions improved and Bulgaria became generally regarded as the most loyal of the Soviet Union's eastern European satellites.

Yugov retired in 1962, and Zhivkov then became Prime Minister and as well as Party Secretary. In 1971, however, he promoted himself to President and made Stanko Todorov Prime Minister. Zhivkov survived the Soviet leadership's transition from Khrushchev to Brezhnev in 1964, and in 1968 again demonstrated his loyalty to the Soviet Union by taking part in the invasion of Czechoslovakia. Although Zhivkov was never a despot in the Stalin mold, by 1981, when he turned 70, his regime was growing increasingly corrupt, autocratic and erratic. This was shown most notably in a bizarre campaign of persecution against the ethnic Turkish minority (10 percent of the population), who were ordered to adopt Bulgarian names: many fled to Turkey, and the issue strained Bulgaria's economic relations with the west.