Wiig joins a cast led by Will Ferrell, who plays the oblivious news anchor Ron Burgundy, and supported by Christina Applegate, Paul Rudd, Steve Carrell and Dave Koechner in the sequel to the 2004 hit, being directed by Adam McKay.
The film, which was announced last March, is due out from Paramount on December 20, the Hollywood Reporter said.
Ferrell and Wiig gave a memorable performance at last month's Golden Globe awards.
She will soon appear in the dramedy 'Girl Most Likely', which she wrote, as well as Ben Stiller's 'Secret Life of Walter Mitty'.
