Allen will play Dollar Bill, a plantation overseer.
Jamie Foxx has the title role of Django, a freed slave who is befriended by a German dentist-turned-bounty hunter. The bounty hunter, played by Christoph Waltz, helps Django free his wife from the evil plantation owner Calvin Candie, played by Leonardo DiCaprio.
Also read: Kurt Russell Poised to Replace Kevin Costner in Tarantino's 'Django' (Exclusive)
In addition to acting, Allen is president of the Austin, Texas-based Presidio Pictures, a film and television production company.
He played a young cop in "48 Hours" and has appeared opposite Robert Duvall in "The Apostle" and "Broken Trail."
"Django Unchained" will shoot in New Orleans and is scheduled to be released on Christmas Day 2012.
Tarantino wrote and is directing the movie.
Stacey Sher, Pilar Savone and Reginald Hudlin are producing.
The Weinstein Co. will release "Django Unchained" domestically. Sony Pictures will handle it internationally.