His publicist, Melissa Booth, says the "Lord of the Rings" director was admitted to Wellington Hospital on Tuesday for severe stomach pains.
Jackson was resting comfortably Thursday and is expected to make a full recovery, according to Booth.
Jackson's illness will delay the start of filming for "The Hobbit," the two-part prequel to the "Lord of the Rings" trilogy. The movies are based on the novels by J.R.R. Tolkien.
The Associated Press contributed to this report.