WC-Co cemented carbides are ceramic-metal composite materials made of carbides embedded in a metal phase that act as a binder. Cemented carbides exhibit an exceptional combination of strength, toughness and wear resistance, but nevertheless are susceptible to abrupt changes in temperature due to its brittle-like nature behavior. Thus, it is well known that thermal cracking and thermal fatigue are recognized as common failure modes in cemented carbides. Our investigation aims to study the thermal shock resistance of two WC-11Wt.%Co cemented carbides with different grain size (fine and ultrafine). In doing so, specimens were subjected to thermal shock by water quenching at different temperatures, ranging from 4000C to 6000C, and at different quenching cycles (1, 3 and 10). Thermal shock resistance is assessed by measuring the retained flexural strength at room temperature. The studied ultrafine-sized hardmetal exhibits slightly higher thermal shock resistance than the ultrafine-sized grade but at the same time is less tolerant to the presence of thermal shock damage due to its lower toughness level. Localized microcracking in the vicinity of the intrinsic critical flaws of the material is suggested as the principal degradation mechanism. Furthermore, elastic modulus is assessed to remain unchanged after thermal shock. This indicates that the abrupt temperature drops do not induce general microcracking in the samples.