It will arrive in a software update, providing extra functionality within the camera app. Selfie portrait mode will provide blurred-background shots - known as Bokeh - using the 16MP front camera on the phones.
The news was actually revealed last week, but it footnoted a blog post (opens in new tab) about the firm's last Open Ears Forum in India so has flown pretty much under the radar until it was spotted by XDA Developers (opens in new tab).
Not the first time
This isn't the first time OnePlus has rolled out features from its latest device to older generations.
There's no word on whether selfie portrait mode will make it to the 3T and 3 - we'd say it's unlikely due to the older chipset inside the phones. We asked OnePlus for more information about the update and when 5 and 5T users can expect it to arrive but a spokesperson was unable to give us any for insight for now.
All they had to say was "we’re always listening to feedback from our users, and are constantly looking for ways we can keep improving their experience."