The 'Woman Like Me' group and the 'Shotgun' hitmaker will be joined by 'Thursday' hitmaker Jess Glynne, 'Addison Lee' rapper Not3s and 'Fine Line' singer Mabel at the hour-long televised show on ITV, where the shortlist for the 2019 ceremony will be unveiled on 12 January from 5pm.
Little Mix are no strangers to the BRITs, having been nominated seven times and winning the award for British Single in 2016 for 'Shout Out To My Ex'.
The programme will also see 2019's BRITs Critics' Choice winner Sam Fender perform and receive the first of Sir David Adjaye OBE's statuettes.
This year sees BBC Radio 1 DJ Clara Amfo replace Emma Willis as host.
She said: ''I am delighted to be hosting 'The BRITs Are Coming'. I've enjoyed the awards since I was a kid, so getting to be part of the excitement with the audience feels great and I can't wait to find out which acts have been nominated in 2019.''
BRITs Chairman and Chairman & CEO of Sony Music UK & Ireland Jason Iley said: ''I am delighted that Clara has agreed to host our nominations show for 2019, she is a fantastic presenter and broadcaster, and the perfect choice for our new prime-time Saturday slot. The line up is a true reflection of the best of British music right now and I am excited to see the performances as we announce the nominations for next year's BRITs.''
The nominations for British Male/Female, British Breakthrough, British Group, British Single, British Artist Video of the Year, International Male/Female, International Group, and the prestigious Mastercard British Album of the Year will be announced on the night.
The BRIT Awards 2019 with Mastercard takes place on February 20 at The O2 arena in London, and will see comedian Jack Whitehall return as the evening's host.