The competing stores said the world's largest retailer has used inaccurate information in recent ad campaigns and filed complaints with state legal officials, according to a Wall Street Journal report.
The retailers argue that the ads cross a line by promoting products the company does not have in ample supply.
A Best Buy spokesman told Reuters on Friday that its legal team has contacted a "handful" of attorneys general in states including Florida, Michigan and Illinois.
Walmart, however, defended its ad campaign to the paper.
"We know competitors don't like it when we tell customers to compare prices and see for themselves," Walmart spokesman Steven Restivo told the Wall Street Journal. "We are confident on the legal, ethical and methodological standards associated with our price comparison advertisements."