Addressing an audience that included many American priests, including Los Angeles Archbishop Jose H. Gomez, the pope referred to the 18th century Franciscan priest as "one of the founding fathers of the United States" and praised his willingness to abandon the comforts and privileges of his native Spain to spread the Christian message in the New World.
FOR THE RECORD: A previous version of this post said that Serra is set to become the first Latino saint. He will be America's first Latino saint.
"I wonder if today we are able to respond with the same generosity and courage to the call of God," Francis said during a homily at Rome's American seminary, the Pontifical North American College.
Francis will formally declare Serra a saint in September during the Washington, D.C., leg of his first visit to the United States. Although the Vatican has canonized Americans before, Serra will be the first saint canonized on U.S. soil.
In California, Serra has been criticized by native American activists for his role in a Spanish colonial system that mistreated and displaced indigenous people, and some have accused him of forcing people to convert to Catholicism. The state Senate voted last month to replace a statue of Serra in the U.S. Capitol with astronaut
Francis did not address directly the controversy in his remarks, but he said the priest was among missionaries "who brought the Gospel to the New World and, at the same time, defended the indigenous people against abuses by the colonizers."
Speaking of missionaries in general, he said, "Sometimes we stop and thoughtfully examine their strengths and, above all, their weaknesses and shortcomings."
The Mass was part of a conference sponsored by the Los Angeles archdiocese in Rome that included clergy and California historians. L.A. Archbishop Gomez told the conference that it was time for "a new conversation" about the mission era and insisted that Serra had "a burning love" for native Americans.
"All of his writings reflect genuine respect for the indigenous people and their ways," he said, according to a statement provided by the archdiocese.
One historian at the conference, professor Robert Senkewicz of Santa Clara University, a Jesuit school, said Serra's canonization shouldn't be seen as proof of perfection.
People "are canonized because they made a commitment which, on balance, had more good than nongood associated with it," Sekewicz said, according to the National Catholic Reporter.
Historian Steven Hackel, author of a 2013 book about Serra, did not attend the conference. He said the pope's words echoed those of Gomez and others who have long defended Serra.
"What they are trying to say is that Serra protected indigenous people from soldiers and settlers and things would have been a lot worse without him," said Hackel, a professor at the UC Riverside. "There's very much truth in that … but the other side of the equation was what did those missions … mean for tens of thousands of Indians."
After Serra died in 1784, conditions worsened and many indigenous people died and much of their culture was lost, Hackel said.