The team didn't say what Bresnahan's duties will be when the hiring was announced Tuesday, but the Bay Area News Group reported that he was expected to become linebackers coach. Coach Hue Jackson, who worked with Bresnahan in Cincinnati, praised him for his motivational skills and ability as a teacher.
Bresnahan spent last season as defensive coordinator for the United Football League's Florida Tuskers. He also has been defensive coordinator for the Bengals and was an assistant coach in Indianapolis and Cleveland.
The Associated Press contributed to this report.