In 1985, Herrmann returned to the University of Michigan as an assistant football coach. He was promoted to the status of a full-time assistant coach at age 29 in December 1989.[8] His responsibilities included linebackers and special teams. In December 1996, following the departure of Greg Mattison, Herrmann took over as Michigan's defensive coordinator.[9] In December 1997, after Michigan completed an undefeated season ranked #1 in the AP Poll,[10] and having led the nation in total yards, scoring and pass efficiency,[11] Herrmann won the Frank Broyles Award as the year's top assistant college football coach.[12][13]
In 2004, the Michigan defense gave up 279 points (23.2 points per game), including 75 points in losses to Ohio State and Texas in the final two games.[14] Criticism of Herrman grew during the 2005 season and became even more heated as Michigan lost five games, compiled its worst record in 21 years, and gave up 244 points in 2005 (20.3 points per game).[15][16][17] In February 2006, Herrmann left Michigan to accept a position as linebackers coach with the New York Jets.[18]The Michigan Daily reported at the time that it was not clear whether "Herrmann chose to leave or fled before [he] could be fired or demoted."[19]
Herrmann served as the linebacker coach for the New York Jets from 2006 to 2008.[20] In January 2009, he was hired as the linebackers coach for the New York Giants.[20] On January 14, 2016, Herrmann was hired as the linebackers coach for the Indianapolis Colts.
In February 2019, he was named associate head coach and linebackers coach for Bowling Green,[21] but instead joined the New York Guardians of the XFL as defensive coordinator.[22]
^"Jim Herrmann's Head". mvictors.com. M Victors. November 10, 2006.("Herrmann steered the M defense into a state of mediocrity after years of adjustments and tweaks ...")