 Under the influence of the collapsing of the Eastern Bloc , on 10 November 1989 the Communist Party gave up its political monopoly , Zhivkov resigned , and Bulgaria embarked on a transition to a parliamentary democracy . The first free elections in June 1990 were won by the Bulgarian Socialist Party ( BSP , the freshly renamed Communist Party ) . A new constitution that provided for a relatively weak elected president and for a prime minister accountable to the legislature was adopted in July 1991 . The new system initially failed to improve living standards or create economic growth — the average quality of life and economic performance remained lower than under communism well into the early 2000s . A 1997 reform package restored economic growth , but living standards continued to suffer . After 2001 economic , political and geopolitical conditions improved greatly , and Bulgaria achieved high Human Development status . It became a member of NATO in 2004 and participated in the War in Afghanistan . After several years of reforms it joined the European Union in 2007 despite continued concerns about government corruption . 
