An improved diethyl ether (DEE) reaction mechanism consisting of 174 species and 973 reactions has been proposed. The present model is derived from an original model of Yasunaga et al. [Yasunaga, K.; Gillespie, F.; Simmie, J. M.; Curran, H. J.; Kuraguchi, Y.; Hoshikawa, H.; Yamane, M.; Hidaka, Y. A multiple shock tube and chemical kinetic modeling study of diethyl ether pyrolysis and oxidation. J. Phys. Chem. A 2010, 114 (34), 9098-9109, DOI: 10.1021/jp104070a]. On the basis of shock tube results in the temperature range of 900-1900 K, pressure range of 1-40 bar, and equivalence ratios of 0.5-2 as well as rapid compression machine (RCM) measurements of a stoichiometric DEE/O-2/inert gas mixture at temperatures of 500-900 K and pressures of 3-4 bar, the ignition delay times (IDTs) were validated. Two-stage ignition at temperatures below 650 K and negative temperature coefficient (NTC) behavior at temperatures between 621 and 746 K are observed. In addition, the freely propagating flame velocities of a stoichiometric DEE/air mixture were validated at various temperatures as well. Using directed relation graph (DRG)-based methods for the improved mechanism reduction, a reduced mechanism composed of 80 species and 329 reactions has been achieved. Calculations for IDTs, laminar flame velocities, and temperature and species profiles using the reduced mechanism show very close agreement with those obtained using the improved mechanism. Meanwhile, sensitivity analyses of the burning velocity and IDT for the improved and reduced mechanisms were performed. Competing reactions related to DEE + OH and consumption of C(2)H(5)OC(2)H(4)s and HO2 were identified as being important for IDTs at various temperatures.