The one-time foreign minister vowed to "respect and defend the constitution, the transition charter and laws and do everything to guarantee justice for all Burkinabes" as he took the oath at a televised ceremony in the capital Ouagadougou.
Poised to formally take over Friday from an interim military ruler, the 72-year-old emphasised his "humility" as a leader aware that he temporarily held "power that belongs to the people".
"The constitution of a country holds the keys to the very organisation of the state. To change it too much leads to a breakdown in society, to regrettable upheavals such as we have recently known," Kafando said.
The landlocked nation of 17 million people "could never become a banana republic," he added, declaring that it was the "first elementary duty of a citizen" to respect the constitution.
Mass unrest erupted in late October over Compaore's bid to change the constitution, which would have allowed him to extend his 27-year rule of the former French colony.
'Awesome responsibility' -
Kafando, who served as Burkina Faso's UN envoy from 1998-2011 and as foreign minister in 1982-83, was chosen to head the transition after tortuous negotiations between the military, political parties and civil society groups.
He is barred from standing in elections scheduled to be held in November next year under the transitional deal.
The African Union had warned that the deeply poor country would face sanctions unless it chose an interim leader, and it welcomed Kafando's appointment.
However, the decision to hand power to a man closely associated with the former regime raised suspicions for many.
"Compaore said for 27 years that he was not thirsty for power, yet he remained firmly in his job," said Amadou Sawadogo, a 37-year-old street seller.
Burkina Faso notably exports cotton and gold, but almost half the population lives on less than one dollar a day and many are subsistence farmers.
"It is an awesome responsibility that falls to me, I already foresee the pitfalls and the immensity of the task," Kafando told reporters after he was named on Monday.
Kafando, who was chosen by a panel of 23 officials, will be charged with appointing a prime minister -- either a civilian or a military figure -- who will head a 25-member transitional government.
A civilian will also head a 90-seat parliament, known as the National Transitional Council.
According to a draft of the blueprint, no members of the interim regime will be allowed to stand in the November 2015 election.
On Tuesday, the United States congratulated the country for forming a transitional government and urged Kafando "to build on the momentum of the past two weeks and to select individuals to serve in the transitional government who are firmly committed to a democratic, civilian government," said State Department spokesman Jeff Rathke.
During the uprising against Compaore, protesters set the parliament building ablaze and attacked other official premises in the capital and other cities in violence not seen since a wave of army mutinies in 2011.
Compaore was 36 when he seized power in a 1987 coup in which his former friend and one of Africa's most loved leaders, Thomas Sankara, was ousted and assassinated.
He held on to power in the following decades, being re-elected president four times since 1991.
His foiled attempt to extend his rule was closely watched across Africa, where at least four heads of state are considering similar tactics to stay in power, from Burundi to Benin and the Democratic Republic of Congo.
Compaore has taken refuge in neighbouring Ivory Coast, where he is living in a luxury villa owned by the state.
Known in colonial times as Upper Volta, Burkina Faso won independence from France in 1960 and changed its name in 1984.
*Source
Yahoo/AFP