[en] Highlights: • Unimolecular thermal decomposition of diethyl carbonate studied at high temperatures. • Measured rates do not exhibit noticeable fall off over 1–3 bar. • Diethyl carbonate decomposition proceeds through ethyl hydrogen carbonate. • Decomposition process results in six-centered retro-ene elimination of ethylene. • Ab-initio/master equation calculations agreed very well with experimental rates. Thermal unimolecular decomposition of diethyl carbonate (DEC) was investigated in a shock tube by measuring ethylene concentration with a CO₂ gas laser over 900–1200 K and 1.2–2.8 bar. Rate coefficients were extracted using a simple kinetic scheme comprising of thermal decomposition of DEC as initial step followed by rapid thermal decomposition of the intermediate ethyl hydrogen carbonate. Our results were further analysed using ab initio and master equation calculations to obtain pressure- and temperature-dependence of rate coefficients. Similar to alkyl esters, unimolecular decomposition of DEC is found to undergo six-center retro-ene elimination of ethylene in a concerted manner.