Objective: To delineate the effect of multiple mild traumatic brain injuries (mTBI) on anger in a military cohort with a well characterized head injury history. Method: 12,270 U.S. Army personnel completed the State-Trait Anger Expression Inventory-2 (STAXI-2). TBI was determined using VA/DoD Clinical Practice Guidelines through self-reported post-traumatic amnesia and loss or alteration of consciousness for lifetime head injuries (up to 6). Lifetime head injury classifications included no TBI history or history of 1, 2, or 3+ mTBI. Results: Kruskal-Wallis test revealed significant between-group differences on all STAXI-2 subtests (p's < 0.001). Consistently, those with no mTBI exhibited less State and Trait anger than those with a history of mTBI; 1 mTBI did not differ from 2 mTBI, but those with 3+ mTBI exhibited more State and Trait anger than those with 1 mTBI. Comparisons between no mTBI and those with 1 or 2 mTBI revealed small effect sizes (Cohen's d) on State (d = −0.23) and Trait anger (d = −0.36). No mTBI versus 3+ mTBI showed a notable increase on both State (d = −0.39) and Trait anger (d = −0.60). Effect sizes were small between those with 1 or 2 mTBI and 3+ mTBI on State (d = −0.16) and Trait anger (d = −0.24). The odds of endorsing clinically significant elevations of anger increased with number of mTBI (1 mTBI: OR = 1.65, 2 mTBI: OR = 1.85, 3+ mTBI: OR = 2.39). Conclusion: Multiple mTBI significantly impact anger experience, expression, and control and increase the risk for clinically significant anger.