Louis Copeland says he has been inundated with phone calls and visitors since Patrick Dempsey dropped into his store yesterday.
The Hollywood star is currently filming the sequel to Disney's Enchanted with Amy Adams in Co Wicklow.
The Disenchanted actor used some of his free time to browse the selection of suits on offer in Dublin's famed Louis Copeland and Sons.
Mr Copeland said he originally intended for it to be a discreet visit, until Dempsey went public.
In a picture shared with his 6.2 million followers on Instagram, Dempsey said he had "a great morning" at the recently reopened shop.
A video of the pair was also shared on Louis Copeland and Sons' account, captioned: "What a pleasure to have McDreamy himself, Patrick Dempsey, into our Wicklow Street store this morning. I'm sure he'll manage to do those suits justice!"
Mr Copeland told Newstalk Breakfast with Susan Keogh about the surreal encounter, and praised the former Grey's Anatomy actor for being "such a nice guy".
"It was all organised a couple of days beforehand and we're doing some stuff for the film itself so we got to know him," he said.
"He arrived yesterday morning and obviously I wouldn't have said it to anybody and I kept it secret.
"We closed off the floor upstairs and nobody knew he was coming in.
"He posted the photograph and normally you would keep these things to yourself but he put it on his Instagram."
The renowned tailor added that business enquiries have been brisk since the visit by one of Hollywood's leading men.
"I can't believe how many phone calls we've had and people actually came down to the stop to look in and see was he still there," he said.
"I have to say he was a pure gentleman, just such a nice guy.
Mr Copeland said Dempsey enjoyed the visit and the atmosphere of being around "normal people".
He couldn't reveal what the actor purchased, only that he was having "a few suits being made".
