The Victoria's Secret model will make her big-screen debut in the undead buddy cop movie starring Jeff Bridges and Ryan Reynolds, according to Heat Vision.
Miller will portray the human avatar of Bridges's character, the dead gunslinger Roy Powell. Miller will therefore be seen when Bridges's dead character is on Earth.
The True Grit star replaced Hangover Part II actor Zach Galifianakis after the 41-year-old departed the film in April.
The film also stars Stephanie Szostak, Kevin Bacon and Mary-Louise Parker.
Miller has previously appeared on the TV series Entourage, Gary Unmarried and How I Met Your Mother.
Based on a comic book by Peter Lenkov, R.I.P.D. is due to open on June 28, 2013.