The Argentine pontiff, a son of Italian immigrants, intends to place the message of the Gospel at the center of the Church's vision, a move expected to resonate with many of the region's faithful, experts said.
It is the pope's first trip to Latin America -- and to the world's largest Catholic nation -- since he was elected pontiff in March.
Faustino Teixeira, a professor of religious sciences at the Federal University of Juiz de Fora in Minas Gerais state, indicated that the visit would carry the message of a fresh start.
"To stem the evangelical growth is not his goal. Francis is more of a pastor, more humble, more of a prophet who rediscovers the church of testimony, coherent with the fundamental values of the Gospel," said Teixeira.
This is in sharp contrast to a church which in the past decades had been characterized by "splendor, doctrinal hot air and seen as a repository of the single truth," he added.
During his week-long visit from Monday, the pontiff will tour a shantytown, a hospital that treats crack cocaine addicts and meet prison inmates.
He will also gather with some of the 1.5 million youths attending World Youth Day (WYD), a major Catholic festival. He wants to be seen as "the pope of the people," sources close to the organizers said. "The pope is not coming to Brazil to proselytize," said Ivan Esperanca Rocha, an expert on religion at the state University of Sao Paulo.
His goal is to defend the "church's social vocation, return to the original church and strengthen the Catholic church."
Some 123 million Brazilians identified themselves as Catholics in 2010 -- 64.6 percent of the total population, compared with 91.8 percent in 1970, according to the latest census figures.
By contrast, evangelicals -- capitalizing on deft use of their own television, radio and social media networks, keep on growing.
With an extensive network of temples in which the faithful have a voice without needing to be ordained pastors, they grew from 5.2 percent of the population in 1970 to 22.2 percent or 42.3 million in 2010.
The pope's message runs counter to what the evangelicals are proposing, said Rocha.
"The evangelical message is linked to results, wealth, success and the church of well-being" while the pope champions the values of St. Francis of Assisi, the 13th century Italian Catholic friar whose name he borrowed and who led a simple life in defense of the poor and close to nature," he added.
In addition, the demands made by hundreds of thousands of Brazilians in nationwide street protests last month -- better public services and an end to rampant corruption -- "dovetail with the message of the pope who will feel right at home," he noted.
Millions of Brazilians who claim to be Catholic do not practice or do so while at the same time following other religions -- such as the Afro-Brazilian Candomble, Umbanda -- or spiritualism.
Religious syncretism is tolerated by a Catholic hierarchy eager to stem eroding support for its faith.
The 2010 census showed a dwindling number of Catholics among those under the age of 30.
Pedro Ribeiro de Oliveira, a professor of religious sciences at the Catholic University of Minas Gerais, attributed the trend to the fact that "over the past 30 years, the Catholic church has become overly clericalized, overly centralized and has turned into a church of priests where laity lacks a voice."
"Liturgy, instead of renovating itself, keeps on stepping backward. Therefore it is difficult to go to mass on Sunday" and parishes "have more and more elderly people and fewer and fewer young people," he added.
Oliveira does not believe Catholics can ever again represent 70 or 80 percent of the population but says they can regain at least some of the lost ground if Pope Francis "succeeds in firing up the church's grassroot -- social and youth -- groups."