McNish will work alongside James Allen for the station, which broadcasts the full season live, except when he has clashes with his Audi World Endurance Championship programme.
Ex-Toro Rosso driver Jaime Alguersuari occupied the 5 Live role for much of 2012.
McNish raced in F1 with Toyota in 2002, but is best known for his sportscar career with Porsche, Toyota and Audi.
The BBC had already announced that Suzi Perry would take over from football-bound Jake Humphrey as the main presenter of its television coverage.
Journalist and broadcaster Tom Clarkson is also joining the TV coverage as a pit reporter, alongside Lee McKenzie.
Ben Edwards and David Coulthard continue as the BBC TV commentators, with Eddie Jordan as a pundit. Gary Anderson will be part of both the TV and radio coverage, while Jennie Gow stays on as 5 Live's pitlane reporter.
The BBC will show half the 2013 F1 season live. Practice sessions for its live races will now be broadcast on BBC2 rather than online and its digital service as before.