The new logo, which they posted on Facebook and Twitter Thursday, does away with the 3D button look and plump font. It's slimmer with a flat "play" button.
It first appeared last week on the redesigned Android and iPhone apps.
The old logo still appears on YouTube's website, so it's unclear whether the new logo will replace the old one or just be an alternative to the original.
YouTube is owned by Mountain View tech giant Google.