The sequel sees Cooper, Helms and Galifianakis on a road trip with no wedding and no bachelor party, unlike the first two movies.
Director Todd Phillips has also revealed that the final instalment in the comedy series will focus on Galifianakis's character Alan as he struggles to cope with the death of his father.
Justin Bartha, Ken Jeong, Jamie Chung, Heather Graham and Mike Tyson will reprise their characters from the series's previous instalments.
The new film also stars John Goodman, who has said that he will be playing "a guy who likes to kill people and dress in track clothes".
The Hangover Part III will be released in the Us and UK on May 24.
Watch Bradley Cooper and Ed Helms discussing The Hangover Part II with Digital Spy below: