The Vatican has said internal migrants should have the same legal protections as refugees, and their children should have the right to birth certificates, education and being reunited with their parents if separated.
The Vatican published a booklet of pastoral guidelines to care for internally displaced people - migrants who are forced to flee their homes because of conflict, natural disasters or persecution but don't cross international borders to seek asylum elsewhere.
More than 40 million people are believed to be displaced within their own countries.
Pope Francis has made the plight of refugees a hallmark of his papacy, calling for countries to welcome, protect, promote and integrate anyone who is forced to leave their home.
The new guidelines apply to internal migrants and lay out ways the Catholic Church can help through advocacy, education, aid and spiritual assistance.
The guidelines call for internal migrants to receive the same UN-sanctioned humanitarian protection as refugees, noting that the same forces, dangers and vulnerabilities are at play.
To avoid new generations of stateless children, the guidelines also call for the Church to press governments to issue birth certificates for children of internal migrants, and say the Church itself can step in to issue its own forms of identification via school documents or baptismal certificates for Catholics.
Amaya Valcárcel, international co-ordinator for the Jesuit Refugee Service, said the key problem about internally displaced people is their "invisibility", and that aid groups often have difficulty reaching them because of government restrictions on access inside their own borders.