The electronics retailer said on Monday its net income fell to $37.4 million, or 30 cents a share in the third quarter, from $49.1 million, or 38 cents a share, a year earlier.
Analysts on average were expecting a profit of 31 cents a share, according to Thomson Reuters I/B/E/S.
Total net sales fell 3.1 percent to $990 million.
Sales at its stores and kiosks open at least a year fell 2.9 percent.
RadioShack had seen an uptick in sales of its converter boxes due to a mandatory switch of all U.S. televisions to digital in June this year. In July, it forecast a decline in the sales of these units in the rest of the year.
The retailer faces a challenging sales environment as consumers tighten their purse strings and curb their appetite for non-essential items in the recession.
It also has to fight fierce competition from national big-box retailers like Best Buy
Earlier this month, Wal-Mart said it will sell discounted mobile services nationwide, threatening to aggravate a price war and hurt profit margins across the U.S. wireless sector.
RadioShack strengthened its merchandise mix by adding popular products such as iPods and iPod accessories. It also signed a deal with T-Mobile USA Inc to expand its wireless offerings.
(Reporting by Dhanya Skariachan; Editing by Derek Caney)