The star of the Guardians of the Galaxy franchise joined a cast made up of hundreds of people for the invitation-only event.
Backed by a huge choir, Pratt told the audience: "About 2,000 years ago, God sent an angel named Gabriel to a city in Galilee named Nazareth to a virgin who was betrothed to a man named Joseph of the house of David.
"That virgin's name was Mary."
He also shared a personal Christmas message about how being a father has taught him more about God's love.
"The way we love our children, the more we love our children, the more we will understand the capacity for our Father in heaven to love us," Pratt said.
"Each and every one of us [is] a precious creation, and He just marvels in the ways that we can try to please Him.
"And through this holiday spirit may we continue to spread peace and goodwill throughout the world. Thank you, and Merry Christmas!"
While Pratt is known for his comedy roles, which are sometimes raunchy with strong language, he regularly shares his faith on social media and in interviews.
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