Voters approved the ban on cockfighting in November 2002.
But dozens of lawsuits claiming that the ban is unconstitutional were filed in district courts.
The Humane Society of the United states and The Fund for Animals applauded the unanimous ruling.
"Now, we should see the end of the barbaric and inhumane practice of cockfighting in Oklahoma," said Wayne Pacelle, a senior vice president of The Humane Society. "No longer will it be legal to pump birds full of stimulants, strap knives to their legs, place them in a pit, and watch them hack one another to death -- all for amusement and illegal gambling."