Sport-related concussions continue to be a serious epidemic for youth participants. A pathway to improper management, created by improper reporting by athletes, lack of recognition by coaches, and lack of access to athletic training services, must be mitigated through effective concussion educational initiatives. The purpose of this study is to investigate the effect of an online concussion education program, "Concussion in Sports," on the knowledge retention among high school football coaches over a 15-week follow-up period. A quasi-experimental repeated measure design was used to measure knowledge retention over time for high school football coaches from two parishes in south Louisiana. The main outcome measure in this study included coaches' knowledge retention in the follow-up period. The assessments consisted of 31 questions divided into three distinct subsections: signs and symptoms recognition, common concussion misconceptions, and scenario-based questions. A 2-tailed paired samples t-test was conducted to test knowledge retention. High school football coaches had significantly lower overall knowledge scores as well as signs and symptoms subsection scores on 15-week follow-up assessments compared to post-course assessments, but the participants did not have significantly lower misconception or scenario subsection scores. This study provides some foundational support that knowledge was not retained in high school football coaches in south Louisiana. This study confirms the need to continue to assess long-term outcomes to assure knowledge retention in high school football coaches after online concussion education.