The Roundabout Theatre Company announced the extension Thursday.
Directed by Michael Longhurst, the limited run -- which was originally scheduled to last through Nov. 25 -- will take a 12-day break before resuming performances Dec. 8. It will then play through Dec. 23.
The show stars Annie Funke, Michelle Gomez, Jake Gyllenhaal and Brian F. O'Byrne. Enid Graham will replace Gomez Oct. 23.
"'If There Is I Haven't Found It Yet' is an entertaining look at a regular family stuck somewhere between knowing what the problem is... and doing something about it," a synopsis said. "Fifteen-year-old Anna's weight makes her a natural target for bullies. When her mom transfers Anna to the school where she teaches in order to protect her daughter, it only makes things worse. Anna's environmentalist dad, determined to finish his new book and save the planet, is no help at all. Just as Anna gets suspended for retaliating with a head-butt, her estranged uncle Terry arrives unannounced."