Vice President Joe Biden was part of the standing-room-only crowd that attended the Palm Sunday Mass at St. Patrick's Cathedral in Midtown, presided over by Cardinal Timothy Dolan.
Palm Sunday marks the start of Holy Week for Christians, which ends on Easter Sunday.
Dolan, the leader of the Roman Catholic Archdiocese of New York, recently returned from the papal conclave in Rome, for the election of Pope Francis.
In his homily, the cardinal focused on his time at the Vatican and the meetings cardinals held before the conclave.
"You know, I just got back from three historic weeks in Rome, and you better get used to hearing a lot of stories about those three weeks," Dolan said.
For many in attendance, it was a thrilling glimpse into a secretive process.
"It was quite an experience, to hear the first-hand stories of how they chose the pope and special inside information we got. It was truly a delight," said one woman who attended.
"He was there being such an important and integral person to that process, and hearing that directly from his mouth, it was really neat," said another attendee.
After the Mass, Dolan and Biden went to have a discussion and some coffee.
Meanwhile, faithful Christians filled churches all over the city, like Our Lady Of Guadalupe in Chelsea.
"This is when Jesus went through Jerusalem and walked the path to Calvary where he was going to be crucified, so Palm Sunday has an extraordinary effect on Christians and Catholics around the world," said a New Yorker.
Many Catholics in the city said celebrating this Holy Week feels a little different.
"Kind of exciting to start Holy Week with the introduction of a new pope and just kind of being able to witness all the festivities and all the events leading up to the election of Pope Francis and being able to partake in his first Holy Week with them," said a worshipper.
Pope Francis held his own Holy Week service in the Vatican, one day after a historic meeting with his predecessor Pope Emeritus Benedict, which was the first meeting between living popes in modern history.