Frank Mansfield (Warren Oates) is a game cock trainer who has taken a vow of silence; he once bragged too loudly about his cockfighting prowess and ended up losing his best fowl in a drunken, late-night match before an important tournament.
To regain his pride after such hubris, Frank refuses to utter a word until he wins the coveted Cockfighter of the Year medal. Cockfighter follows his ups and downs as he attempts to succeed in the shadowy, barely legal sport.
Frank loses his truck, trailer, and a girlfriend after trying to rig a match with fellow cocksman Jack Burke (Harry Dean Stanton), and has to sell his house to raise funds for stock.
Later, Frank wins ten roosters in a private backwoods match and trains them heavily with his partner, Omar Baradinsky (Richard B. Shull), working his way back to the top of his chosen craft.
He also attempts to reestablish his relationship with an old girlfriend (Patricia Pearcy) who doesn't know much about cockfighting and is repulsed when she actually witnesses one in the flesh. There is plenty of brutal footage included in Cockfighter that will dismay many animal lovers, so those with qualms about the sport should steer clear.