They are the first class of the Africa leadership programme run by The Obama Foundation.
He has repeated the message he made yesterday while giving the annual Mandela lecture - that he was inspired by Nelson Mandela to serve.
He told the young people that he was also inspired by the work they were doing in their communities.
Mr Obama says he knew while he was still president that he wanted to return to Africa to help its young people build networks, as he says it is through networks that people are able to build communities and his foundation wants to help to bridge that gap.
Wednesday marked exacly 100 years when Nelson Mandela was born.
In South Africa, the former US President Barack Obama marked the centenary on Tuesday with a speech in which he warned that the politics of fear was spreading fast across the world.
A century after his birth, and five years after his death, Nelson Mandela is still inspiring people, and still provoking debate. Read Full Story