The firm's first ever quarterly loss, thanks to slow Wii sales and poor 3DS adoption rates, led to the slide in stock value, according to Bloomberg.
Nintendo's largest shareholder, former president Hiroshi Yamauchi, has lost $500 million (£307m) as a result.
Nintendo has since reacted by downsizing its financial profits forecast by 82% for the coming quarter.
Yesterday, Nintendo announced that the price of the Nintendo 3DS will drop by a third across the globe, a move that is unprecedented for the company so soon after a new hardware launch.
In addition to the 3DS price cut, Nintendo is giving 3DS early adopters ten NES and ten Game Boy and Game Boy Advance games free exclusively before other users.
The Nintendo 3DS price cut follows a disappointing launch, with less than half a million systems sold in both the US and Japan.
The European launch was more successful, breaking the sales records of both the Wii and DS for the region.