The two have been at odds since the presidential election in August, which the nation's highest court nullified over poll irregularities.
Odinga later boycotted the repeat vote in October,
saying the electoral commission had not implemented any reforms.
The joint appearance Friday is the first time Kenyatta and Odinga have met publicly since the election, Kenyan media reported.
It comes the same day US Secretary of State Rex Tillerson is expected to arrive in Kenya on his first official trip to Africa, which includes visits to Ethiopia, Nigeria and Djibouti.
During their joint address in the capital of Nairobi, the two Kenyan officials said they're putting the past behind them.
"We have come to a common understanding, an understanding that this country of Kenya is greater than any one individual," Kenyatta later tweeted. "For this country to come together, leaders must come together."
Odinga echoed the sentiment, saying the joint address was to discuss issues affecting Kenya and send a message that "dissent stops here."
"We have resolved that the future (of) our nation is more important than any sole individual," he said on Twitter.
Kenyatta was declared the winner of the October repeat election with 98% of the vote. Activists tried to stop the election after Odinga boycotted the vote and urged his supporters not to take part.
As tensions between the two dragged on, clashes broke out in the extended election period, with dozens of people killed,
according to the Kenya National Commission on Human Rights.
In January, Odinga swore himself in as the "people's president" at a mock inauguration ceremony in Nairobi. At the time, his party said it wanted to create an alternative government to protest Kenyatta's rule.
But the government warned the inauguration amounted to treason -- an offense punishable by death under Kenyan law.
Ahead of the mock swearing-in, the government turned off four private television stations
-- a move not seen in the country in years.
Tillerson was to meet with Kenyatta on Friday and hold a news conference later.
"As we look ahead, this administration seeks to deepen our partnership with Africa, with an aim of making African countries more resilient and more self-sufficient," Tillerson said this week.
"That serves our partners, and it serves the United States as well by creating a stable future for all of our children and our grandchildren. "