"I thank in the name of the Lord God even my keepers, who have been understanding to me and who have not hurt me. It's God's intervention," an emotional Thomas Uzhunnalil, 59, said after emerging from 18 months in captivity.
"The best weapon against any enemy is love and prayer," he said at a press conference in Rome after an intervention by the authorities in Oman to secure his release.
He was abducted in March 2016 during an attack on a care home operated by missionaries in the southern port city of Aden which killed 16 people, including four nuns.
Muscat said Tuesday that it had "coordinated with Yemeni parties" to mediate the release of Uzhunnalil, a Salesian priest who had last appeared in a video circulated online in December 2016, in which he appealed to Prime Minister Narendra Modi and Pope Francis to secure his release.
The Vatican has said that Uzhunnalil, a diabetic who lost 30 kilos (66 pounds) during his ordeal, will spend time recuperating in Rome after a medical check-up.
He met Wednesday with Pope Francis, who had described the Aden attack as "senseless and diabolical".
Yemeni authorities blamed the ISIS group for last year's attack, though no group has yet claimed responsibility for the abduction.
Al-Qaeda, which is also active in the area, has appeared to distance itself from the mass shooting, saying it was not involved.
The internationally recognised government in war-torn Yemen is grappling with both an Iran-backed rebellion and a growing jihadist presence.
Uzhunnalil, who had been running three Catholic churches in Yemen, said he had been abducted essentially for being in the wrong place at the wrong time.
"They did not know me. I happened to be in that place," he said, adding that the attackers "left me in peace and killed the others -- perhaps they wanted money."
"After the killing of the sisters they put me into the car. They spoke Arabic, I didn't understand them," he added, but "I was not afraid. I was not trembling. I prayed to God to be merciful."
"I was not mistreated. They have not injured me at all," added Uzhunnalil, who said he did not know if a ransom had been paid.
He also said that the apparent aggression towards him in the video he appeared in was seemingly for show.
He said that his attackers, rather than abuse him, "didn't try to force me -- but they said 'when you are free, back home, read the Koran and become a Muslim'."