Mladenov was born to a peasant family in the village of Toshevtsi, Vidin Province on 22 August 1936.

[citation needed] Mladenov served as the first secretary of the party's committee in Vidin Province from 1969 to 1971.

At the yearly Warsaw Pact summit, he met with Mikhail Gorbachev and got his tacit support for removing Zhivkov.

[3] In October 1989, Mladenov organized a 35-nation environmental conference and invited the Bulgarian NGO Ecoglasnost to participate.

Ten days into the conference, several Ecoglasnost members were beaten up by the Darzhavna Sigurnost (secret police) and the militia on orders from Zhivkov.

On 9 November, just after he returned from a trip to China, Mladenov and his colleagues persuaded Zhivkov to resign (under threat of execution), which he did the next day.

[3] Mladenov was then elected to Zhivkov's old posts as general secretary of the party and chairman of the State Council.

[2] In his first address to the Central Committee as the country's leader, he stated that there was "no alternative to restructuring" both the economy and the political climate, which in their previous forms had "handicapped progress in our society in all spheres".

[2] Despite Mladenov's promises of reforms, the people took to the streets almost every day to demand greater freedom.

[9] Mladenov underwent a heart bypass in Houston in 1986, leaving him in frail health in the ensuing years.