Garrett, a former Heisman Trophy winner, has held the school's athletic director post for 17 years. Garret received much criticism for his handling of the scandals surrounding USC's football team and other programs during his tenure.
The NCAA hit USC with severe sanctions last month, including a two-year bowl ban and scholarship restrictions.
Haden has resigned his post on the USC Board of Trustees to take his new position. During his time on the Trojan's football team during the 1970s, Haden led his team to three Rose Bowl appearances and two national titles.
After graduating from USC in 1975, Haden made the Los Angeles Ram's' roster in 1976 as a quarterback.
AP contributed to this report.