To compare sex differences in alexithymia (poor emotional processing) in males and females with traumatic brain injury (TBI) and uninjured controls. Cross-sectional study. TBI rehabilitation facility in the United States and a university in Canada. Sixty adults with moderate to severe TBI (62% men) and 60 uninjured controls (63% men) (N=120). Not applicable. Toronto Alexithymia Scale-20 (TAS-20). Uninjured men had significantly higher (worse) alexithymia scores than uninjured female participants on the TAS-20 (P=.007), whereas, no sex differences were found in the TBI group (P=.698). Men and women with TBI had significantly higher alexithymia compared with uninjured same-sex controls (both P<.001). The prevalence of participants with scores exceeding alexithymia sex-based norms for men and women with TBI was 37.8% and 47.8%, respectively, compared with 7.9% and 0% for men and women without TBI. Contrary to most findings in the general population, men with TBI were not more alexithymic than their female counterparts with TBI. Both men and women with TBI have more severe alexithymia than their uninjured same-sex peers. Moreover, both are equally at risk for elevated alexithymia compared with the norms. Alexithymia should be evaluated and treated after TBI regardless of patient sex.