Thomas Lewis Jones, who runs Hafod Hardware in Rhayader, with his grandparents, created the promotional video with the help of family and friends.
Watch the advert here:
It features his young son Arthur as he goes about the shop helping customers, carrying out handiwork and putting up Christmas decorations.
The ad then ends with Arthur transforming into his father, with a slogan encouraging visitors to “be a kid this Christmas”.
After the video received over 50,000 views on YouTube within two days, Mr Jones told the PA news agency: “It has been crazy… we’ve been overwhelmed with nice emails and messages from all over the world.”
“The only thing we had to pay for was getting our singer into the music studio and paying the sound engineer.
“Everyone you see in the video is my family, there’s four generations featured in the video and it was made with the help of my best friend Josh Holdaway, who is a filmmaker.”
The store opened its doors in 1895, and Mr Jones has worked there for 10 years.
He told PA: “We’ve done adverts for the last two years, this is the third instalment, Arthur features in all the adverts.
“This year we wanted to just do something that was quite simple to film that had a nice message and story.
“People have been coming in this morning saying congratulations… they’ve been bringing in bottles of champagne for us to say well done.
“The locals are incredible, they’re our bread and butter, we’re very lucky to have the community we have here in Rhayader.”
Mr Jones said their aim was to encourage people to shop locally over Christmas.
He said: “The underlying message is that small independent businesses can offer you just as much as your large high street chains.
“Try and shop locally over Christmas if you can.”