CAR has been torn apart by violence between Muslim rebels and Christian militias.
The Pope was speaking after arriving in the capital, Bangui.
Acting President Catherine Samba-Panza has asked him for “forgiveness” for the country’s recent religious violence.
Large crowds lined the road from the airport to welcome the Pope – and people cheered and sang when he arrived at a refugee camp.
In an address at the presidential palace, he called for unity and to avoid “the temptation of fear of others, of the unfamiliar, of what is not part of our ethnic group, our political views or our religious confession”.
The Pope said ahead of his trip he was determined to bring a message of peace and hope to the country.
During the visit, the pontiff will celebrate Mass in Bangui, but is also expected to meet Muslim leaders and visit a mosque in the city’s Muslim enclave, known as PK5.