Mattox coached as an assistant for two seasons at Emmanuel following his graduation, helping them go 49–21 from 2011 to 2013.[2] He then served as a graduate assistant for the Morehead State Eagles from 2013 to 2015, was their director of basketball operations from 2015 to 2016, and was an interim assistant coach in the 2016–17 season, before receiving a promotion to full-time assistant coach in 2017.[2][4]
After having served from 2017–18 to 2020–21 as an assistant, Mattox was promoted to associate head coach for the 2021–22 season.[5] He helped them win the Ohio Valley Conference (OVC) title in 2021 with a runner-up position in 2022.[6] After one season as associate head coach, Mattox was hired away to be an assistant for the Murray State Racers.[6][7]
Following two seasons at Murray State, Mattox was named the head coach of Morehead State on April 5, 2024.[8][9]