Lawmakers voted 120-97 to elect 53-year-old Oresharski, a former finance minister not associated with any party, to head the Cabinet.
In a separate vote, legislators also approved the Cabinet itself — a 15-member government of technocrats supported by the Socialist Party and a mainly ethnic Turkish party, the Movement for Rights and Freedoms.
Oresharski promised to bring stability, economic growth and a normal business environment to the cash-strapped country, which now has 14 per cent unemployment rate and the lowest average wages in the European Union. About 22 per cent of the population lives below the official poverty line.
"The country is in a deep institutional crisis, continuing economic depression and worsening disintegration of society," Oresharski told Parliament before he was elected. He also called for more solidarity "in a society shaken by despair and lack of prospects."
Oresharski has announced that he will keep the currency board regime that pegs the national currency, the lev, to the euro, and curtails its central bank monetary operations.
He also said that he would keep the flat 10-per cent income tax, as well as a 10-per cent corporate tax, despite calls for an increase by the Socialists.
Potential energy-price cuts and an overhaul of the ailing health care system are also on Oresharski's agenda, as well as increasing social benefits for the poor and families with young children. He plans to raise money for his immediate goals by restructuring budget spending but without widening the deficit above the planned level of 1.3 per cent of GDP for this year.
Oresharski appointed Zinaida Zlatanova as his deputy in charge of justice and home affairs, and the absorption of EU funding on which the country relies heavily. Zlatanova was the former head of the EU delegation in Sofia.
New finance minister will be Petar Chobanov, a former chairman of the country's financial regulator.
Kristian Vigenin, a European Parliament member, will be the new foreign minister, and Angel Naidenov will head the ministry of defence.