The pundit, who became as well know for his rapping skills as his performances in midfield for Watford and Liverpoool in the 1980s and 1990s, will enter the house on Friday to join housemates including Amanda Barrie, Ann Widdecombe and Jess Impiazzi.
The announcement was made by host Rylan Clark-Neal on spin-off show Big Brother’s Bit On The Side as New Order hit World In Motion, which Barnes appeared on when it was released for the 1990 World Cup, played out.
Dancing around with a football, Clark-Neal said: “Sing it for England. You don’t get more testosterone here than him.”
Panellist Kate Lawler also jumped out of her seat, expressing her excitement at the new addition to the house.
Barnes managed Celtic briefly between the summer of 1999 and February 2000. He also had spells in charge of Tranmere Rovers and the Jamaican national team.
On Tuesday night, eight women entered the house as part of an all-female special series launch.
Marking 100 years since women won the right to vote in the UK, the show’s first contestants this year include: former Coronation Street actress Amanda Barrie, former Tory MP Ann Widdecombe, ex-Made In Chelsea star Ashley James, newsreader India Willoughby, reality TV star Jess Impiazzi, former detective constable Maggie Oliver, novelist and journalist Rachel Johnson, and Malika Haqq, best friend of Khloe Kardashian and series regular on the family’s US hit show.
Barrie and Impiazzi earned immunity from the first Celebrity Big Brother evictions by winning the series’ first task moments after entering the house.
Emma Willis returns live to the house on Friday at 9pm on Channel 5 to introduce the male housemates.