Fox will star opposite Jon Hamm, Kristen Wiig, Adam Scott and Westfeldt herself.
Friends With Benefits revolves around a pair of thirtysomething best friends who observe the toll that having kids has taken on the couples they know and resolve to bypass that stress by having a child and then date other people.
Hamm will produce alongside real-life partner Westfeldt, with Mike Nichols and Jake Kasdan on board to executive produce.
Kasdan said of the film:
“Jen wrote one of the funniest and most original scripts I’ve read in a long time, the rare great generational character comedy.”