Nintendo has shifted 2m copies of Mario Kart 8, according to a shareholder that had attended the company's annual general meeting.
The business also said Wii U sales have increased significantly following the game's launch, although did not provide figures.
Wii U is at a critical point in its history. The machine has so far failed to generate a significant enough install base to warrant significant support from publishers or retailers.
But the recent performance of Mario Kart 8, plus a successful E3 showing, suggests it might not be quite game over for Nintendo's home machine.
Nintendo's AGM was held by general hardware manager Genyo Takeda and game creator Shigeru Miyamoto. Satoru Iwata did not attend after recovering from an operation.