The video streaming service tweeted on Tuesday night, stating it was aware of reported problems on the site and with products YouTubeTV and YouTube Music.
"We're working on resolving this and will let you know once fixed," the tweet said, in part.
The site went down shortly after 6 p.m. and remained out for more than an hour. Users reported it coming back up by around 7:40 p.m.
The cause of the issue was not stated by the company.
YouTube, owned by Google's parent company, is the second most popular site on the Internet, behind only Google itself. The company estimates a billion hours of content are watched on YouTube every day.