Acupressure is a complementary and alternative medicine (CAM) treatment using fingertips to stimulate acupoints on the skin. Although suggested to improve cognitive function, acupressure has not been previously investigated with a controlled design in traumatic brain injury (TBI) survivors, who could particularly benefit from a non-pharmacological intervention for cognitive impairment. A randomized, placebo-controlled, single-blind design assessed the effects of acupressure (eight treatments over 4 weeks) on cognitive impairment and state of being following TBI, including assessment of event-related potentials (ERPs) during Stroop and auditory oddball tasks. It was hypothesized that active acupressure treatments would confer greater cognitive improvement than placebo treatments, perhaps because of enhanced relaxation response induction and resulting stress reduction. Significant treatment effects were found comparing pre- to post-treatment change between groups. During the Stroop task, the active-treatment group showed greater reduction in both P300 latency (p = 0.010, partial η² = 0.26) and amplitude (p = 0.011, partial η² = 0.26), as well as a reduced Stroop effect on accuracy (p = 0.008, partial η² = 0.21) than did the placebo group. Additionally, the active-treatment group improved more than did the placebo group on the digit span test (p = 0.043, Cohen's d = 0.68). Together, these results suggest an enhancement in working memory function associated with active treatments. Because acupressure emphasizes self-care and can be taught to novice individuals, it warrants further study as an adjunct treatment for TBI.