"#NintendoSwitchOnline will launch in the second half of September," it wrote. "The service provides access to online play & Save Data Cloud backup in compatible games and a growing library of NES titles with added online play."
Nintendo didn't immediately respond to a request for further comment.
It'll cost $20 a year (around £15 or AU$30), with options to pay $3.99 per month, $7.99 for three months or $34.99 for family group -- which allows the account holder to invite up to seven others to join that group.
Online play has been free on the Switch since it launched in March 2017, but it will be part of the paid service once it hits in September. That applies to use of the voice chat-enabling Online app, available on iOS and Android, as well.
Subscribers will also get access to 20 free NES games -- including Donkey Kong, Super Mario Bros. 3 and The Legend of Zelda -- which will have online play for the first time, cloud saves and various other special offers.
You're going need to subscribe if you want to play Fortnite for Switch or online games of Super Smash Bros Ultimate, which revealed new fighters and features in a Nintendo Direct stream on Wednesday and arrives on Dec. 7 (check out our guide for more details).
Nintendo Switch sales nearly hit 20 million at the end of July -- with games like Donkey Kong Country: Tropical Freeze and Mario Tennis Aces doing particularly well -- and the company's new president, Shuntaro Furukawa, won 96.5 percent approval from the company's shareholders in June.
Watch this: Here's why Super Mario Odyssey is so freaking great