The popstar and Voice judge will have her locks cut down to 0.5mm for a 'Big Dare' to raise money for the charity.
[Jessie J prepares for Red Nose Day]
"Shaving my head for charity is something I've promised to do for a long time and Comic Relief has given me the opportunity to try and raise as much money as possible for good causes by doing it," said the 'Price Tag' popstar.
"I've loved watching Red Nose Day since I was a kid and I'm so excited to join this year's team of celebrity 'fun raisers' and help support the campaign.
"So this Red Nose Day I'll be shaving my head live on the night of TV! I won't deny that I'm nervous but I am also honoured to be part of this year's campaign.
"Together with help from the UK public, we are on a mission to raise more money than ever before for Red Nose Day. So come on, let's do it!"
Red Nose Day is celebrating its 25th anniversary this year and the TV celebrations will take place on Friday, March 15.
Michael McIntyre, Rob Brydon, John Bishop, Zoe Ball, Lenny Henry, Davina McCall, Nick Grimshaw, Jonathan Ross and Claudia Winkleman will be among the presenters across the evening
[Caroline Flack and Claudia Winkleman prepare for Red Nose Day]
Comedy across the evening will include sketches from Call the Midwife, Rowan Atkinson, Fresh Meat and Russell Howard's Good News.
Stella McCartney has designed Red Nose Day T-shirts, which have been modelled by Caroline Flack, Stephen Fry, Miranda Hart, David Walliams, Jack Whitehall and Claudia Winkleman. They are available to buy from TK Maxx nationwide, tkmaxx.com and rednoseday.com.
One Direction are releasing this year's official Red Nose Day single, a cover of Blondie's 'One Way Or Another', and Melanie C, Jack Dee, Chelsee Healey, Phillips Idowu, Greg James and Dara Ó Briain are currently taking part in this year's BT Red Nose Day Challenge - a trip down the Zambezi River to Victoria Falls.
Watch Jessie J discuss shaving her head for Red Nose Day below: