Purpose Serious head injuries, also known as traumatic brain injuries (TBIs), are associated with an increase in aggression and violent tendencies. The current study extends the literature on head injuries by examining whether gang membership is associated with an elevated risk of head injury in prison, and the extent to which this relationship is mediated by different forms of prison violence. Methods We use data from the LoneStar Project, a representative sample of 802 men imprisoned in Texas. We assess the gang membership-head injury link using logistic regression and Karlson-Holm-Breen (KHB) mediation. Results Prison gang members were >2.5 times as likely to report a head injury in prison compared to non-gang members (OR = 2.593; 95% CI = 1.220–5.509), net of controls. KHB mediation analyses reveal that violent misconduct and violent victimization collectively reduced the magnitude of the relationship between gang membership and in-prison head injury by 34.84%. Conclusions Prison gang members have a higher risk of head injury in prison, which we demonstrate is largely a function of their increased involvement in prison violence. Cognitive behavioral therapy (CBT) interventions should be used to lessen the negative repercussions from head injury and would be beneficial for reentry preparation.