This study presents a detailed investigation into the gas-phase thermal decomposition of tetrabromobisphenol A (TBBA), that is, the most widely used brominated flame retardant (BFR). Elimination of one of the methyl groups characterizes the sole dominant channel in the self-decomposition of the TBBA molecule at all temperatures. A high-pressure rate constant for this reaction is fitted to k(T) = 2.09 × 1010T1.93 exp( -37000/T) s-1. The high A factor and low activation energy for this reaction arise from the formation of a delocalized radical upon the loss of a methyl group. We calculate rate constants for the bimolecular reactions of TBBA with H, Br, and CH3 radicals. Kinetic and mechanistic data provided herein should be instrumental to gain further understanding of the fate of TBBA during thermal degradation of materials laden with this BFR.