The tech giant has confirmed its inventory of handsets has gone, and advised customers wanting to buy one of the phones should check in with other retailers while supplies still last.
As reported by Android Police, the product pages for both devices now redirect to the online store's homepage, while any other mentions of the phone say they're out of stock.
The development comes a year after the company removed the Pixel 2 from its store.
Google is preparing to launch the Pixel 4A - the follow-up to 2019's Pixel 4 phone - and the device is set to go on sale for around $399.
Late last year, the company updated the Pixel 4's Face Unlock feature to allow the smartphone to "recognise" the owner's face "better over time" thanks to an improvement in the Pixel Features Drop.
Google states: "When it's on, face unlock images are occasionally used to create improved face models.
"This helps recognise you better over time."
The Face Unlock works even if a person has their eyes closed.