The American singer songwriter with a hugely loyal fan base, nick named Grobanites, tweeted in Irish after the show.
He said: "DUBLIN!!! you made me feel like this kid tonight. Go raibh maith agaibh agus slán go fóill!!"
Groban played at the 14,000-capacity amphitheater located at the North Wall Quay, in Dublin City's Docklands. Among his song choices for the evening was the old Irish favorite "She Moved Through the Fair".
Last week the Hollywood Reporter announced that the LA singer, known for his sense of humor, would be joining Charlie Day and Danny DeVito in the cast of "It's Always Sunny In Philadelphia".
Here's a clip of Groban doing a skit on "Jimmy Kimmel Live" singing Kanye West's Twitter updates: