His films include Chicken Run, The Rescuers Down Under, James and the Giant Peach, Over the Hedge, The Spiderwick Chronicles, Charlotte's Web, and The Hitchhiker's Guide to the Galaxy.

Kirkpatrick wrote the English-language screenplays for the U.S. releases of the Studio Ghibli films The Secret World of Arrietty in 2012 and From Up on Poppy Hill in 2013.

He went to become a freelance screenwriter, and his early writing credits include Honey, We Shrunk Ourselves, James and the Giant Peach, and The Little Vampire.

Kirkpatrick had a longstanding relationship with DreamWorks Animation, where he has contributed as a writer or story consultant on The Road to El Dorado and Madagascar.

In May 2006, DreamWorks Animation released Over the Hedge, for which Kirkpatrick co-wrote the screenplay and made his directorial debut, sharing directing credits with Tim Johnson.

Kirkpatrick wrote the English-language screenplay for the U.S. releases of the Japanese animated films The Secret World of Arrietty in 2012 and From Up on Poppy Hill in 2013, both of which were produced by Studio Ghibli.