The 48-year-old actress, who co-starred in Showtime's Weeds last year, filed for divorce on Nov. 15 in Los Angeles Superior Court, citing irreconcilable differences.
Leigh, whose movie credits include Fast Times at Ridgemont High, Last Exit to Brooklyn and Single White Female, is seeking spousal support and primary custody of their 7-month-old son, Rohmer, with visitation for Baumbach.
Baumbach, 41, met Leigh in 2001 when she was starring in the Broadway play Proof. They married in September 2005.
The pair collaborated twice during their marriage: Leigh starred in Baumbach's 2007 directorial effort, Margot at the Wedding, and they co-wrote the 2010 Ben Stiller film Greenberg, which Leigh also starred in.