The roll-out to over two-thirds of the home and garden retailer's stores follows a successful pilot at two locations.
Furry friends will be able to browse all areas of the participating stores except for food aisles.
A spokesman for Wilko said: "A pet is more than just a pet, they're family.
"That’s why we've decided to welcome pets in-store at 248 of our locations
"We hope that shoppers will enjoy bringing their furry friends along with them."
Signage at store entrances will make it clear if pets are welcome, although customers can also check with the store team if they are unsure.
Service dogs remain welcome at all stores nationwide.
Following Wilko's announcement on Facebook, nearly 8,000 people commented on the post, but not everyone was happy about the news.
One person said: "I like dogs but don't particularly want them around me in a shop.
"Lots of people are afraid of dogs, and being in a confined space with them isn't going to be a pleasant experience.
"Plus, I'd be afraid of stepping on paws if the dogs gets too close."
Another pointed out that some shoppers could be allergic to dogs.
They wrote: "Not a good move for people with allergies.
"Unless it's a guide dog or specifically trained assistance dog I don't think it's necessary."
A third customer said: "What about the people like myself who have severe allergies to them?
"I'll definitely not be able to shop there anymore."
Others welcomed the move and were happy to hear their dogs would be allowed in certain stores.
One customer said: "My dog is my family. I hate going out without her.
"She's like my support dog."
Another wrote: "Brilliant. [I] wish all shops would do this."
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