The actress will be playing a gambling addict forced to look after her adult daughter, according to The Hollywood Reporter.
Wiig will take on the role of the playwright daughter, who is placed in her mother's custody after unsuccessfully attempting to get her ex-boyfriend's attention with a fake suicide attempt.
The film will be directed by Shari Springer Berman and Robert Pulcini, who previously helmed comic adaptation American Splendor.
Bening is currently attached to the indie comedy He Loves Me, which will also star Steve Coogan.
She will play the worried mother of a talented young novelist who is studying from crippling writers' block, only to have a dream girl from his writing come to life".
He Loves Me features Paul Dano in the lead role, with Steve Coogan appearing as a rival author.
Bening received an Oscar nomination this year for The Kids Are Alright, in which she plays a woman whose long-term lesbian partner cheats on her with the biological father of their children.
Watch Annette Bening in the trailer for The Kids Are Alright below:
See Kristen Wiig talk about Bridesmaids with co-star Rose Byrne below: