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Subradiance is the cooperative inhibition of the radiation by several emitters coupled to the same electromagnetic modes. It has been predicted by Dicke in 1954 and only recently observed in cold atomic vapors. Here we address the question to what extend this cooperative effect survives outside the limit of frozen two-level systems by studying the subradiant decay in an ensemble of cold atoms as a function of the temperature. Experimentally, we observe only a slight decrease of the subradiant decay time when increasing the temperature up to several millikelvins, and in particular we measure subradiant decay rates that are much smaller than the Doppler broadening. This demonstrates that subradiance is surprisingly robust against thermal decoherence. The numerical simulations are in good agreement and allow us to extrapolate the behavior of subradiance at higher temperatures.Understanding the influence of decoherence or dephasing processes in cooperative effects such as super-and subradiance [1-7] is not only interesting from a fundamental point of view, but it is also important for the possible developments of photonic device exploiting cooperativity in the classical or quantum regime [8][9][10][11][12][13]. This is especially true if one wants to use solid-states devices [14,15], which are subject to phonon-induced decoherence. Previous theoretical studies of various toy models in the framework of open quantum systems have predicted some robustness of superradiance to noise and dephasing [16][17][18].In this Letter, we report an experimental study of thermal decoherence of subradiant Dicke states in large ensemble of cold atoms [4]. Indeed, even if laser-cooled atoms are not coupled to phonons, they are not completely frozen. Atomic motion has been shown to be a source of decoherence for coherent back-scattering [19] and to suppress the effect of recurrent scattering on the refractive index of dense atomic media [20,21]. Since subradiance is an interference effect involving very long time scales, it is expected to be particularly fragile.On the contrary, and quite surprisingly, we show here that subradiance in the linear-optics regime is robust against thermal motion. We observe only a slight decrease of the subradiant decay time when increasing the temperature up to several millikelvins, and in particular we measure subradiant decay rates Γ sub that are much smaller than the Doppler broadening Γ D , given by the width of the atomic velocity distribution. We also perform numerical simulations showing that the breakdown of subradiance only occurs when the Doppler broadening is on the same order of magnitude as the natural lifetime of the atomic transition Γ 0 . In practice, this means that subradiance can be observed and used at any "coldatom" temperature and even beyond.The experimental setup is based on a cloud of cold 87 Rb atoms prepared in a magneto-optical trap (MOT). After 60 ms of loading from the background vapor and a stage of compressed MOT (30 ms) we obtain a sample of N ≈ 3 × 10 9 atoms at a temperatu...