Uhuru Kenyatta has won the 2017 presidential election.
The President got 8,203,290 votes, while rival Raila Odinga got 6,762,224, IEBC chair Wafula Chebukati said on Friday.
"I wish to declare Uhuru president-elect and William Ruto deputy president-elect," he said amid cheers.
Uhuru, who was earlier at KICC, received his certificate while thanking the commission chair.
The crowd erupted, singing 'Twasema asante', shortly after which Uhuru was invited to address the gathering.
NASA boycotted the announcement earlier on Friday saying their concerns have not been addressed.
After days of ghost towns, tedious vote counting and varied opinions by NASA and Jubilee, Uhuru has been granted another five years as Kenya's ruler.
Kenyans waited anxiously as tallying was done, supporters of Opposition leader Raila Odinga clearly showing they wanted him to win on his fourth try.
They held protests and celebrations as the National Super Alliance addressed several press conferences.
Despite NASA's boycott, the announcement was attended by various dignitaries, including US Ambassador Robert Godec, JP secretary general Raphael Tuju and Cabinet Secretaries Amina Mohamed (Foreign Affairs) and Najib Balala (Tourism).
Uhuru will receive his certificate from the commission and there will not be much protocol as his security is already in place.
It is expected that the Opposition will issue a statement on their way forward as Raila and his running mate Kalonzo Musyoka (Wiper) have not accepted defeat.
Uhuru had been leading the interim tally but Raila's NASA party declared him winner.
They even demanded that the electoral agency name Raila president, saying his votes numbered 8.04 million and Uhuru's 7.7 million.
By 11 am on Friday, the commission's portal showed Uhuru had 8,170,016 votes (54.26 per cent) and Raila 6,754,173 votes (44.85 per cent).
NASA CLAIMS "RIDICULOUS"
Celebrations broke out in pockets of Kenya on Thursday after the opposition said Raila should be declared winner, a claim an election commission official said was "ridiculous".
Hundreds of supporters, mainly young men, poured onto the streets of the opposition stronghold of Kisumu in celebration. At least one truck of anti-riot police followed them, a Reuters witness said. Some older men tried to convince the youth not to join the crowds.
There were pockets of similar celebrations in opposition strongholds in Nairobi as well.
After complaining of fraud, the Opposition chief told Reuters he believed most of more than 20,000 polling station result forms uploaded to the election commission's website were fake.
He said results were being filled out by agents working out of a Nairobi hotel but he did not provide any evidence. He previously said the election commission's computer network had been hacked and that results were "fictitious".
A senior official in the election commission rejected the claim.
"They have done their own additions and they think Raila has eight million (votes), which is ridiculous, there is nothing," Abdi Guliye said. "As far as we are concerned, we don't believe they have any credible data."
Later the commission provided a detailed rebuttal of the opposition claims, pointing out mathematical errors and saying documents purporting to be from their system "were plainly falsified and contain elementary errors."
"WE DON'T WANT TO FIGHT"
Uhuru, a 55-year-old businessman seeking a second five-year term, and Raila, 72, loser of Kenya's last two elections amid similar claims of fraud, are the heads of Kenya's two political dynasties.
Earlier in the week, Raila urged his supporters to remain calm but warned: "I don't control the people."
The US State Department urged any candidate challenging the result to do so in accordance with the "constitution and rule of law and not through threats or acts of violence", while also urging candidates to "peacefully and patiently" await official results.
International observers have said the election was free, fair and credible.
"It would be very regrettable if anything emerges afterwards that sought to corrupt the outcome, to spoil that outcome," said Thabo Mbeki, the former South African president in charge of the African Union observer mission
Many members of the public say they just want their normal lives back.
"We don't want to fight," said Kisumu driver Evans Omondi, 28, wearing a polo shirt and jeans. "We want to go back to work."
In 2007, tallying was halted and the incumbent president declared the winner, triggering an outcry from Raila's camp and waves of ethnic violence that led to International Criminal Court charges against Uhuru and Ruto.
The cases against them collapsed as witnesses died or disappeared.