Ethiopia's new leader, Hailemariam Desalegn, has been sworn in after the death of long-time leader Meles Zenawi in August.
"I am very happy to take the responsibility of being prime minister," said Mr Hailemariam, 47, as lawmakers banged on their desks in support, AFP news agency reports.
Mr Hailemariam had been deputy prime minister and foreign minister.
Mr Meles died last month in Brussels after 21 years in power.
He had been praised for bringing economic growth to Ethiopia but criticised for not tolerating opposition.
He was also a key Western ally in the volatile Horn of Africa - twice sending troops into neighbouring Somalia to tackle Islamist groups.
Mr Hailemariam was last week chosen to head the governing Ethiopian Peoples' Revolutionary Democratic Front (EPRDF).
He vowed to continue Mr Meles' "legacy without any change".
"We brought peace, democracy and development to the country," he said.
Technician, not fighter
BBC Africa analyst Martin Plaut says Mr Hailemariam would appear to be an unlikely man to lead the country.
He is from the small Wolayta community in the south, rather than the northern elites who have traditionally ruled Ethiopia.
He is a Protestant, not an Orthodox Christian, as many Ethiopian Christians are.
Professor Chris Clapham from Cambridge University in the UK says Mr Hailemariam was chosen as the late prime minister's deputy to give the government ethnic balance.
Ethiopia's new leader is a technician, not a fighter, like the man he replaced, our correspondent says.
An engineer by training, Mr Hailemariam studied in Finland and the United States.
He became a university dean before entering politics, rising to become president of the Southern Nations, Nationalities and Peoples Region.
Mr Hailemariam led the Southern Ethiopia People's Democratic Movement, part of the EPRDF. But commentators point out this is the least influential member of the alliance.