Harrell got his start in coaching at his alma mater, as Howard's wide receivers coach from 2002 to 2003. He served as wide receivers as
Texas Southern University from 2004 to 2005 and then at
Florida A&M University from 2006 to 2007. In 2008, Harrell was the quarterbacks coach at
Morgan State University in
Baltimore. While at Morgan State he also served as the wide receivers coach for Team Michigan, of the
All American Football League (AAFL) in 2008. Harrell then spent to two seasons, from 2009 TO 2010, as the
offensive coordinator at
Bowie State University in
Bowie, Maryland. Harrell returned to Howard in 2011 as head football coach. In 2012, he was honored by the D.C. Touchdown Club as the Local College Coach of the Year at its inaugural awards dinner. Harrell took a leave of absence in 2013, but returned as Howard's head coach in 2014. In five seasons as Howard's head coach, Harrell compiled a record of 20–36 including a 7–4 mark in 2012. Harrell joined
Lane Kiffin's coaching staff at
Florida Atlantic University in January 2017 as wide receivers coach. Under Harrell's tutelage, senior Kalib Woods was named the MVP of the
2017 Conference USA Football Championship Game. Willie Wright, a freshman, was the team's most consistent wideout and led the Owls with 56 catches and a total of six scores. Following the year, Wright earned a spot on the C-USA All-Freshman team. In 2019, Harrell served as assistant head coach and running backs coach for at
Alabama State University. Harrell joined
Jackson State University in November 2020 as the team's running backs coach under
Deion Sanders. In December 2022, Harrell followed Sanders to the
University of Colorado Boulder to be the assistant head coach and running backs coach for the
Colorado Buffaloes. In January 2025 it was announced that Harrell left the team. In April 2025, Harrell was announced as the running backs coach at the University of Wyoming. ==Personal life==