Regional leaders and foreign diplomats are expected to arrive at Kenya's national football stadium on Tuesday, with musicians, dancers and a military parade entertaining an estimated 60 000 people.
But long before dawn, buses arrived from across the country, packed with supporters from central Kenya and the Rift Valley, heartlands of Kenyatta's Kikuyu people and of his soon to be vice-president William Ruto.
Ruto, like Kenyatta, also faces trial at the International Criminal Court (ICC) in The Hague for crimes against humanity over their alleged role in planning 2007-2008 post-election violence.
Security was heavy as Kenyatta loyalists, dressed in the red colours of the winning Jubilee Coalition party, waved as military bands played tunes to welcome the new leader and say farewell to outgoing President Mwai Kibaki (81) retiring after more than a decade in power.
"This is a great day," 23-year-old student Martin Munyua told Agence France-Presse. "People thought Uhuru could not be president but we showed them that we believe in him. This is our day to celebrate."
Kenyatta and Ruto are due to be sworn into office by Kenya's Chief Justice Willy Mutunga at 11 am, according to the country's Constitution.
'Welcome our new sons'
"We have come to welcome our new sons to the State House," said 35-year old high school teacher Jairus Koech, who travelled throughout the night from the Rift Valley town of Eldoret to attend the celebrations.
Kenyatta (51), who is one of Africa's richest men, won the March 4 polls by more than 800 000 votes ahead of his nearest rival, outgoing Prime Minister Raila Odinga.
Odinga and civil society groups filed legal challenges alleging the polls were marred by a series of irregularities that skewed the results.
However, Kenya's Supreme Court last month unanimously ruled the election had been fair and credible and that Kenyatta and Ruto had been "validly elected".
Last month's polls were peaceful apart from isolated incidents, avoiding a repeat of the ethnic killings and widespread violence that followed the 2007 polls, when more than 1 100 people were murdered and several hundred thousand forced to flee their homes.
Odinga is reported not to be attending the ceremony, and newspaper editorials on Tuesday warned that Kenyatta would face a tough task ahead to unite Kenya.
Challenge uniting Kenya
"Fortunately the country remained peaceful during the elections, but unfortunately many still feel disenfranchised," the Star newspaper editorial read, warning it is important "to unite the country".
"A sense of national unity, patriotism, belonging and pride will only come about with a very deliberate programme to heal the septic ethnic wounds that so pollute our politics," the Daily Nation read.
"We hope that magnanimity in victory will be reciprocated by grace in defeat."
Heads of state of Kenya's neighbours are expected to attend, including Ethiopia's Hailemariam Desalegn, South Sudan's Salva Kiir, Tanzania's Jakaya Kikwete and Uganda's Yoweri Museveni.
Other leaders due to attend include South Africa's Jacob Zuma, Nigeria's Goodluck Jonathan, Democratic Republic of Congo's Joseph Kabila and Zimbabwe's Robert Mugabe.
Western nations, many of whom have a policy of only "essential contact" with ICC indictees, are expected to send ambassadors.
China is due to send Zhang Baowen, National People's Congress standing committee vice-chairperson.
Alleged roles in the violence
Sudanese President Omar al-Bashir, who faces an ICC arrest warrant for genocide, is not expected to attend.
The new president and Ruto (46) both face potentially lengthy trials at the ICC for their alleged roles in the violence that followed disputed elections in 2007.
Kenyatta, in his acceptance speech when he was announced the winner of the election, promised to work with the international community but said pointedly he would also expect they should "respect our sovereignty".
Both he and Ruto have said they will cooperate fully with the ICC.
Kenya, as a signatory of the Rome Statute of the ICC, would be supposed to act on any arrest warrant issued by the court should the pair refuse to attend trial. – AFP