Mica Craig, of Clarkston, Wash., was at the store Saturday looking for mulch, saw what he thought was a stick blocking the aisle and picked it up with his right hand, the Lewiston Tribune reported.
"I picked up that stick, it bit me and I started screaming," Craig said.
Craig said he managed to shake off the snake -- estimated to be 1-to-1 1/2 feet long -- did "a tap dance on it and got it killed."
Someone called 911 but fellow shopper Maria Geffre, who witnessed the incident, said there wasn't time to wait for an ambulance and took Craig to a hospital.
After observation at the emergency room, Craig was released because doctors said they did not believe the snake injected venom, he said. But when he got home, Craig said, his hand grew to the size of a cantaloupe.
He returned to the hospital and was given anti-venom for the bite. Doctors also cut his hand open to relieve some of the swelling.
"They got all the poison out of me but they don't know how bad the muscle damage will be," Craig said.
"My hand feels like it's in a burning fire right now," he said Sunday.
A Walmart manager said he could not confirm or deny the snakebite incident, the Tribune reported.