Chan Shingadia, born in India, and her husband Hash, who run the convenience store in Middleton's hometown village of Bucklebury, southern England, were among several local workers who received gold-embossed invitations to Britain's wedding of the year.
The village's butcher and postman are also on the guest list.
Chan Shingadia, 42, said Middleton visited the store "two or three times a week" when she was at home with her parents in the village, some 50 miles west of London.
"We've been here for 13 years, and we've really got to know Kate. She is really caring. She is like a human being, not a celebrity, and she is always a good customer," Chan said.
Prince William often comes along, too, so the store keeps a reserve of his favorite ice cream -- mint-flavored Viennetta -- just in case he drops by. Chan Shingadia also makes sure there is a good supply of Haribo candy, which is liked by the royal couple.
Bucklebury butcher Martin Fidler and his wife Sue, postman Ryan Naylor and John Haley, landlord of a local hotel where Middleton and the prince sometimes go for drinks, were also invited to the April 29 wedding.