After the announcement, Mr Kenyatta called for unity, telling opposition supporters: "I reach out to you... We are all citizens of the same republic".
But the opposition rejected the results even before they were declared, calling the process a "charade".
However it has been endorsed by international observers. Mr Kenyatta said they had ensured a "free, fair and credible election".
Earlier, Mr Odinga's supporters said he had won, and published their own figures. The electoral commission said this was "illegal and premature", and said basic mathematical errors had been made.
Many observers fear a repeat of the violence after the disputed election 10 years ago when more than 1,100 Kenyans died and 600,000 were displaced
Opposition rejection
Shortly before the results were announced, opposition members said they will reject it."We are not going to be party to it. Our issues have not been addressed. One can conclude they [electoral commission] are not keen on taking our concerns seriously," Musalia Mudavadi, a senior official of the National Super Alliance (NASA) and former Kenyan vice president, said.
James Orengo, another senior NASA official, called the election process a "charade" and a "disaster".
"You do not just hold an election for the sake of it. And the election is not about announcing winners and losers," he said.
On Wednesday, Odinga - a long time rival of Kenyatta who was running for the presidency for the fourth time - rejected the results of Tuesday's election.
He claimed the country's electronic voting system had been hacked and the results were doctored.
In a bid to unite the country after the heated campaign, Kenyatta reached out to Odinga and his supporters, saying, "We are not enemies".
"We are all citizens of one republic. As with any competition, there shall always be winners, and there shall be losers. But we all belong to one great nation called Kenya. I extend a hand of friendship."
Previous disputes
Chebukati, the electoral commission chairman, said a hacking attempt had failed to manipulate the outcome of the vote. International observers including the African Union said the election was free and fair and called on disputes to be resolved through the courts.In 2013, Odinga lost to Kenyatta and claimed the results were manipulated but Kenya's Supreme Court announced Kenyatta the winner.
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