Purpose: The prevalence of traumatic brain injury (TBI) among offender populations is significantly higher than among the general population. Despite this, no study has yet assessed the knowledge of members of the probation service surrounding traumatic brain injury (TBI). Method: Knowledge was assessed among members of the Probation Board for Northern Ireland (PBNI) using a cross-sectional online version of the Common Misconceptions about TBI (CM-TBI) questionnaire. Mean total misconception scores, along with scores on four subdomains (recovery, sequelae, insight, and hidden injury) were calculated. Analysis of variance was used to explore differences in misconceptions based on the collected demographic information. Results: The overall mean percentage of misconceptions for the group was 22.37%. The subdomain with the highest rate of misconceptions (38.21%) was insight into injury which covered misconceptions around offenders’ self-awareness of injuries. Those who knew someone with a brain injury scored significantly higher in the CM-TBI total score (F(1,63)= 6.639, p = .012), the recovery subdomain (F(1,63) = 10.080, p = .002), and the insight subdomain (F(1,63) = 5.834, p = .019). Additionally, significant training deficits around TBI were observed among the probation service. Conclusions: This study is the first of its kind to examine the level of understanding around TBI within probation services. The findings reflect potential barriers to identification and rehabilitation of TBI for offenders coming into contact with the criminal justice system. A lack of identification coupled with misconceptions about TBI could lead to inaccurate court reporting with a subsequent impact on sentencing.