Worldwide sales of Nintendo's latest games console slumped to just 160,000 in the last three months.
Financial results posted by the Japanese company show the Wii U has sold 3.61 million units since it launched last November.
However, it was even outsold by the original generation Wii over the last six months, with 660,000 sales to the Wii U's 550,000.
The Wii U console features the GamePad controller, a tablet-type device which allows users to continue playing even after the connected television has been turned off or switched to another channel.
It received mixed reviews after its launch, with concern surrounding the amount of games available to justify the cost.
Nintendo sold more than three million Wii U consoles in the third quarter of 2012/3, which included the company's peak Christmas period.
However, sales fell to just 390,000 in the following three months.
Software sales for the Wii U were at 1.03 million between April and June compared to 1.7 million in the previous quarter, as the company posted a net income of 8.6 billion yen (£57.7 million).
The video games industry has suffered in recent years due to the rise of smartphones and other devices that offer online entertainment.
Nintendo said it plans to launch several new games for the Wii U in order to boost console sales.
Titles due for release include The Legend of Zelda: The Wind Waker HD, Donkey Kong Country: Tropical Freeze and Super Mario 3D World, as well as Wii Party U and Wii Fit U.