Omega-3 fatty acids (ω − 3 FAs) attenuate inflammation and improve neurological outcome in response to traumatic brain injury (TBI), but the specific anti-inflammatory mechanisms remain to be elucidated. Here we found that NLRP3 inflammasome and subsequent pro-inflammatory cytokines were activated in human brains after TBI. Rats treated with ω − 3 FAs had significantly less TBI-induced caspase-1 cleavage and IL-1β secretion than those with vehicle. G protein-coupled receptor 40 (GPR40) was observed to be involved in this anti-inflammation. GW1100, a GPR40 inhibitor, eliminated the anti-inflammatory effect of ω − 3 FAs after TBI. β-Arrestin-2 (ARRB2), a downstream scaffold protein of GPR40, was activated to inhibit inflammation via directly binding with NLRP3 in the ω − 3 FAs treatment group. Interestingly, we also observed that ω − 3 FAs prevented NLRP3 mitochondrial localization, which was reversed by GW1100. Furthermore, ω − 3 FAs markedly ameliorated neuronal death and behavioral deficits after TBI, while GW1100 significantly suppressed this effect. Collectively, these data indicate that the GPR40-mediated pathway is involved in the inhibitory effects of ω − 3 FAs on TBI-induced inflammation and ARRB2 is activated to interact with NLRP3.