ObjectiveTo examine the spectrum and severity of cognitive symptoms in veterans with migraine, traumatic brain injury (TBI), or both; and to evaluate the extent to which psychiatric conditions contribute to the relationship of migraine and TBI with cognitive symptoms.BackgroundMigraine contributes significantly to global disability, with veterans facing additional burdens due to high comorbidity of TBI and psychiatric conditions. Understanding the intersection of these conditions is crucial for improving veterans’ health‐care outcomes.MethodsThis observational study used self‐reported data from 338,217 veterans enrolled in the Million Veteran Program (MVP) to assess cognitive symptoms using the Medical Outcomes Study Cognitive Functioning Scale Revised (MOS‐Cog‐R) and psychiatric conditions in veterans with migraine only, TBI only, both, or neither.ResultsOf the participants, 30,080/338,217 (8.9%) veterans reported migraine, 31,906/338,217 (9.4%) reported TBI, and 7828/338,217 (2.3%) reported both migraine and TBI. Veterans with only migraine or only TBI reported similar levels of cognitive symptoms (M = 74.19, standard deviation [SD] = 25.18; M = 73.87, SD = 24.98, respectively), which were substantially higher than veterans without these conditions (M = 62.52, SD = 27.90). Veterans with both conditions reported the most cognitive symptoms (M = 83.01, SD = 22.13) and psychiatric conditions (depression = 5041/7828 [64.4%], anxiety = 3735/7828 [47.7%], post‐traumatic stress disorder = 4243/7828 [54.2%]). The association of migraine and TBI with cognitive symptoms persisted beyond the influence of psychiatric conditions (B = −2.20, standard error = −0.36, p < 0.001).ConclusionVeterans with migraine reported cognitive challenges analogous to veterans with TBI, indicating a need for careful attention to cognitive symptoms in veterans with migraine. Further, the associations of migraine and TBI with cognitive symptoms in veterans were not explained by psychiatric conditions. These findings encourage future research to elucidate the association between self‐reported and objective cognitive symptoms and to identify factors, including environmental exposure and genetic influences, contributing to cognitive impairment to optimize the assessment and treatment of veterans with migraine.