Hilltop Honey, based in Caersws, will sell its raw wildflower and creamed honey in 650 stores.
Founder Scott Davies said the deal will double his business scope and full-time workforce of six.
"Four years ago I walked into Newtown to sell my first four jars of honey and now I'm supplying at least 24,000 jars to Tesco. It's incredible," he said.
"There is currently no raw honey on the shelves so it's really good for consumers, for British honey and for British beekeepers and bees."
A beekeeper from Powys who started out selling honey from his parents' kitchen has secured a deal to supply Tesco.