Pope Francis denounced extremists around the world who in his words are "perverting" religion to justify violence.
On arriving in Albania's capital on Sunday, the pope said, "Let no one consider themselves to be the `armor' of God while planning and carrying out acts of violence and oppression."
The pontiff praised the Balkan nation as an "inspiring example" where Christians and Muslims endured brutal oppression under communism, but now live and work peacefully together.
Security was unusually tight for the Pope's 11-hour visit to the majority Muslim country, his first visit to a European country outside of Italy.
The Roman Catholic leader celebrated Mass before about 250,000 people in Mother Teresa square in Tirana and met with Albanian President Bujar Nishani.
Large portraits of Catholic priests and nuns who were persecuted under communism have been hung on the boulevards leading to Mother Teresa Square.
The revival of Catholicism in Albania is due in part to the popularity of Mother Teresa, who was born in what is now Macedonia, but had Albanian origins.
Under Stalinist dictator Enver Hoxha, who declared Albania the world's first atheist state in 1967, hundreds of priests and imams were jailed and scores executed before the regime fell in 1990.
Nearly 2,000 churches, Orthodox and Catholic, were destroyed under Hoxha, as well, with many being turned into cinemas or dancing halls.
Muslims make up about 59 percent of Albania's population, with Catholics amounting to 10 percent and Orthodox Christians just under that, according to the country's official figures.
President Nishani thanked Pope Francis for making the country his first European destination, saying it was a historic event for all Albanians.
Nishani said, "There is no intolerance, extremism among us but reciprocal respect inherited from generation to generation. From an atheist country, we have turned into a country of religious freedom.''
Earlier, aboard the plane taking him on the short trip across the Adriatic from Rome to Tirana, Pope Francis said he wanted to visit Albania because it had “suffered very, very much.”
He is the first pope to visit Albania in 21 years.
Both the Vatican and Albanian officials dismissed media reports of concern for the pope's safety. Security appeared normal for a papal trip overseas and in some places lighter than in some previous trips.
Pope Francis returned to Italy Sunday night, after his brief one-day visit to Albania.
Some material for this report came from Reuters and AP.