Most experts speculate that this was done in an attempt to hide their "pagan" religion from their masters who had forbidden them to practice it. To say that Haitian Vodou is simply a mix of West African religions with a veneer of Roman Catholicism would not be entirely correct. This would be ignoring numerous influences from the native Taíno Indians, as well as the evolutionary process that Vodou has undergone shaped by the volatile ferment of Haitian history. It would also be ignoring the large influence of European paganism in Roman Catholicism and its pantheon of saints.

Vodou as we know it in Haiti and the Haitian diaspora today is the result of the pressures of many different cultures and ethnicities of people being uprooted from Africa and imported to Hispaniola during the African slave trade. Under slavery, African culture and religion was suppressed, lineages were fragmented, and people pooled their religious knowledge and out of this fragmentation became culturally unified. In addition to combining the spirits of many different African and Indian nations, pieces of Roman Catholic liturgy have been incorporated to replace lost prayers or elements; in addition images of Catholic saints are used to represent various spirits or "mistè" ("mysteries", actually the preferred term in Haiti), and many saints themselves are honored in Vodou in their own right. This syncretism allows Vodou to encompass the African, the Indian, and the European ancestors in a whole and complete way. It is truly a "Kreyòl" religion.

The most historically important Vodou ceremony in Haitian history was the Bwa Kayiman or Bois Caïman ceremony of August 1791 that began the Haitian Revolution, in which the spirit Ezili Dantor possessed a priestess and received a black pig as an offering, and all those present pledged themselves to the fight for freedom. This ceremony ultimately resulted in the liberation of the Haitian people from French colonial rule in 1804, and the establishment of the first black people's republic in the history of the world.

Haitian Vodou grew in the United States to a significant degree beginning in the late 1960s and early 1970s with the waves of Haitian immigrants fleeing the Duvalier regime, taking root in Miami, New York City, Chicago, and other major cities.

Survivals in the Southern US

A common saying is that Haiti is 80% Roman Catholic and 100% Vodou. In the southern United States, it has also influenced the system of folk magic and folk religion known as hoodoo which derives primarily from Congo and Angolan magical practices from Central Africa. The best survivals of possibly Haitian-influenced religion in the southern US, however, are most likely to be found within the African-American Spiritual Churches of New Orleans, a Christian sect founded by Mother Leafy Anderson in the early 20th century which incorporates Catholic iconography, ecstatic worship derived from Pentecostal forms, and spiritualism. A hallmark of the New Orleans Spiritual Churches is the honoring of the Native American spirit named Black Hawk.