One guard was killed and 20 people were injured in the May 20 riot at the privately-run Adams County Correctional Facility in Natchez, which holds illegal immigrants convicted of crimes in the U.S.
A filing Friday in U.S. District Court in Natchez says Yoany Oriel Serrano-Bejarano plans to change his plea to guilty.
A complaint filed by an FBI agent says he assaulted a guard and helped other inmates climb onto the roof of a building where correction officer Catlin Carithers was beaten to death.
At least one other inmate has pleaded guilty in the case. Juan Lopez-Fuentes was sentenced to more than three years.