The former Strictly Come Dancing star will join comics Frank Skinner and Rhod Gilbert to offer her verdict on the eight celebrity acts performing in the charity dance-off.
"I'm thrilled to be joining the panel on the Let's Dance final this Saturday night and looking forward to the run-ins with Rhod and Frank in deciding who has danced that extra mile for Sport Relief!" said Phillips.
The acts and the routines they will be performing in the grand final are:
Terry Alderton - Tina Turner 'Proud Mary'
Tameka Empson and Laurie Brett - Lady GaGa and Beyoncé 'Telephone'
Eddie 'The Eagle' Edwards - Austin Powers 'Soul Bossa Nova'
Miles Jupp - The Prodigy 'Firestarter'
Tyger Drew Honey and Dani Harmer - Bugsy Malone 'Fat Sam's Grand Slam'
Omid Djalili - Public Enemy 'Fight The Power'
Rowland Rivron - Fatboy Slim 'Weapon Of Choice'
Fatima Whitbread and The Cuban Brothers - The Bee Gees 'You Should Be Dancing'
Katy Perry is the special guest musical act and JLS will also be in the studio performing their Sport Relief single 'Proud'.
Let's Dance airs on Saturday (March 17) at 7.10pm on BBC One.
> Katy Perry to perform on 'Let's Dance' final
Watch the music video for upcoming JLS single 'Proud' below: