The slide came after media reports that a replacement for its aging Switch console will be delayed.
A new device had been expected later this year, but now reportedly won't come until 2025.
The Switch has been a massive hit for Nintendo.
Earlier this month the firm even raised its sales outlook for the console.
Its lifecycle has been extended by a string of hit games, including last year's new "Legend of Zelda" title.
But it's coming up to eight years on the market, and is widely seen as in need of an update.
Nintendo has never revealed its plans for a successor, beyond saying that it is always working on new hardware and software.
Last week, Japanese rival Sony slashed sales forecasts for its PlayStation 5 console.
That followed weaker-than-expected sales over the holiday shopping season.
