Sunday's celebration commemorates the day Jesus made a triumphant entry into Jerusalem.
In Los Angeles, the Cathedral of our Lady of Angels in downtown hosted a Palm Sunday mass.
One service was given with Archbishop Jose Gomez and another with Rev. David Gallardo.
Both masses began outdoors for the blessing of palm branches - a tradition since the fourth century.
Meanwhile, thousands of people waved palm and olive branches Sunday morning in St. Peter's Square in Vatican City.
Pope Francis gave a two-hour service - leading the world's Catholics into Holy Week.
He asked the crowd to pray for peace ahead of Easter, which is next Sunday.