Banda, a 61-year-old women’s rights activist and education campaigner, was due to be sworn in as president later on Saturday in the Chinese-built National Assembly in the capital Lilongwe, officials said.
She will become southern Africa’s first female head of state.
The government only officially confirmed 78-year-old Mutharika’s death earlier on Saturday, two days after he had died following a heart attack.
His body had been flown to a military hospital in South Africa.
The delay in the announcement had raised worries about a political crisis because Banda had been expelled from Mutharika’s ruling DPP party in 2010 after an argument about the succession, though she retained her state position.
Dispelling fears of a power struggle, Banda appeared at a news conference in the capital Lilongwe to declare 10 days of official mourning for Mutharika, who had ruled for eight years. She ordered national flags to be flown at half-mast and the state broadcaster to play somber music.
“I call upon all Malawians to remain calm and to keep the peace during this time of bereavement,” Banda said, flanked by members of the cabinet, the attorney general and the heads of the army and the police.
“As you can see, the constitution prevails,” she said, wearing a colorful black, silver and pink robe and headdress.
The constitution stipulates that the vice-president takes over if the president dies, but Mutharika appeared to have been grooming his brother Peter, the foreign minister, as his de facto successor.
In a sign that Banda had support across the political spectrum, opposition leaders called for her to be swiftly sworn in as head of state and some 20 members of the national governing council of Mutharika’s Democratic Progressive Party (DPP) also expressed their backing for her.
Banda is expected to run the country until scheduled elections take place in 2014.
The streets of the main cities Lilongwe and Blantire were calm on Saturday, though police guarded strategic locations.
There appeared to be little public sorrow at Mutharika’s death. Many of Malawi’s 13 million people had viewed him as an autocrat personally responsible for an economic crisis that stemmed ultimately from a diplomatic row with former colonial power Britain a year ago.
“A woman president is something new for us. A lot of people really never thought about it. But most people would rather have Joyce Banda than Peter Mutharika,” said a security guard in Blantire who gave his name only as Chisomoa.
The presidency and cabinet issued a statement assuring citizens and the international community “that the constitution of the Republic of Malawi will be strictly adhered to in managing the transition.”
Both Britain and the United States, major donors to Malawi until they froze millions of dollars in aid over rows with Mutharika over his policies and actions, urged a smooth transition respecting the constitution.
Britain and others froze aid worth some 40 percent of government spending, fuel supplies dried up and food prices soared, leading to popular unrest and attacks on Mutharika’s economic policies by bodies as diverse as the Catholic Church and the International Monetary Fund.
“It’s sad that he is leaving behind so many unsolved problems,” said Stella Mataka, a waiter at a lodge near Blantyre’s Chileka International airport.
As reports of the death of the self-styled “Economist in chief” swept the capital, there were bursts of drunken jubilation among those who accused Mutharika of turning back the clock on 18 years of democracy in the “Warm Heart of Africa.”
Medical sources said Mutharika’s body was flown to South Africa because Malawi’s energy crisis was so severe the Lilongwe state hospital would have been unable to conduct a proper autopsy or even keep his body refrigerated.
“We as government will be in consultation with the bereaved family, advise the date when our president’s body will arrive from South Africa and other funeral arrangements,” Banda said.
“I also want to ask all Malawians to join me in wishing that the soul of our president rests in peace,” she added.
