Posttraumatic stress disorder (PTSD) is a condition characterized by avoidance, reexperiencing, hyperarousal, mood, and cognition issues, following a traumatic experience. Pharmaceutical treatments have limited effectiveness, creating interest in alternative treatments for PTSD. Current evidence suggests that PTSD is associated with glutamate excitotoxicity, oxidative stress, and neuroinflammation, collectively known as the neurotoxic triad. Dietary interventions have shown benefit by treating one or more aspects of the neurotoxic triad. Antioxidant and anti-inflammatory micronutrients and phytochemicals have shown benefit for improving PTSD symptoms. Additionally, the low glutamate diet, which eliminates exposure to dietary excitotoxins, while also increasing micronutrients protective against the neurotoxic triad, has been shown to significantly improve PTSD in veterans with Gulf War Illness, with an effect size greater than first-line pharmaceuticals, and no adverse effects. Diet may be uniquely suited to treat PTSD by reducing the neurotoxic triad. More research is needed to confirm and expand upon these findings.