The multibillion dollar-settlement included a $6.6 billion payment, plus a temporary reduction in interchange fees, a gesture valued at about $1.2 billion, The Wall Street Journal reported.
However, "The proposed settlement (with Visa Inc., MasterCard Inc. and others) would not structurally change the broken market or prohibit credit card networks from continually increasing hidden swipe fees," Wal-Mart said in a statement.
The company urged "all merchants to put consumers first and reject the settlement."
Target and the National Association of Convenience Stores have also rejected the deal, which would cancel the retailers' rights to sue for similar issues in the future, a major complaint among those rejecting the settlement, the Journal said.
"It's a very real possibility that there could be a snowball effect. You do have two of the largest retailers speaking out against the settlement, which is significant," said David Robertson, publisher of the payment industry newsletter the Nilson Report.
Walmart and Target speaking up against the deal could overturn it. The deal allows the credit card companies to back out if stores representing 25 percent of credit car sales volume reject it.