Matt Wood was fired after clocking in late for lunches, the Durango Herald reported Monday.
Supporters said his wife, Jessica Wood, should have been notified of the problem because she is his representative on employment issues and best-suited to help him address issues.
Jessica Wood said she had good relations with former managers at the store, but changes occurred and eventually communication was lost.
New managers cited problems with Wood's time management, so she said she took away his electronic book and cellphone to avoid distractions.
Wood suffered a brain injury in 2005 during his junior year at Utah Valley University, when he was involved in a car crash.
Wal-Mart spokeswoman Kayla Whaling said the company takes such cases seriously.
"We are currently looking into the situation further, and we'll handle it appropriately once we know more," Whaling said.
Jessica Wood said Wal-Mart knew of her husband's challenges and that accommodations needed to be made when they hired him in 2008, the newspaper said.
"The two biggest things that we wanted were that he be able to revolve his work schedule around the bus, which they were very good at, and that I, as his wife and representative, be notified whenever anything needed to be discussed regarding him," she said.