The series is based on the UK show by the same name and written by Lena Dunham and Jenni Konner, reported Variety.
The series has an eight-episode order from HBO and both Dunham and Konner are executive producing it via their company A Casual Romance.
It follows a group of people as they come together to celebrate Kathryn's husband Walt's 45th birthday over a weekend spent back in nature, before it becomes a weekend of tested marriages and woman-on-woman crime.
Garner will play the role of Kathryn Siddell-Bauers, which has been described as "messy, tough and provocative and really really fun".
"We love Jennifer's restraint and comedic timing, and we cant wait for the warmth and intelligence she'll bring to our central character, Kathryn. It's truly a dream to have her first on our call sheet. Now we just have to write her some stunts," said Denhum and Konner
This will be television outing for Garner ever since her Emmy-nominated run as CIA agent Sydney Bristow on "Alias", which aired from 2001 to 2006.