Best Buy warned of an increasingly promotional environment heading into the holidays and promised to be competitive on price in the biggest selling season of the year, raising concerns about margins in the fourth quarter.
Earlier on Tuesday, discounter Wal-Mart Stores announced it will match select Black Friday offers on toys and electronic items from rivals Target, Toys R Us, and Best Buy starting as early as a week before the big shopping day.
(Read more: Wal-Mart ups the ante on Black Friday yet again)
"If our competition is in fact more promotional in the fourth quarter, we will be too and that will have a negative impact on our gross margin," Best Buy Chief Financial Officer Sharon McCollam said in a statement.
The news overshadowed the better-than-expected quarterly profit from the world's largest consumer electronics chain in the third quarter and dragged its shares down 6.6 percent.
Under Chief Executive Officer Hubert Joly, who took the retailer's helm last fall, the company has cut costs by removing layers of management, eliminating hundreds of jobs and closing some unprofitable stores. It has also boosted cash by selling its stake in a European joint venture with Carphone Warehouse Group.
Best Buy's net earnings were $54 million, or 16 cents a share, compared with a net loss of $10 million, or 3 cents a share, a year earlier.
(Read more: Home Depot ups outlook again after strong quarter)
Excluding restructuring charges and other items, it earned 18 cents a share, up from 3 cents a share in the year-earlier period and beating the average analyst estimate of 12 cents, according to Thomson Reuters I/B/E/S.
After the earnings announcement, the company's shares fell in pre-market trading. (Click here for the latest quote.)
Revenue decreased to $9.36 billion from $9.38 billion a year ago.
Analysts had expected the company to report earnings excluding items of 12 cents a share on $9.36 billion in revenue, according to a consensus estimate from Thomson Reuters.
The CNBC information in this article was updated to show Best Buy's revenue decreased to $9.36 billion from $9.38 billion a year ago.
—By Reuters. CNBC contributed to this report.