This paper's primary objective is to analyse the physiological (cortisol) and behavioral responses of military working dogs (MWD). Dogs (N=27) were submitted twice to environmental challenges (challenge 1 and 2, 20 days in-between) composed of social (training), visual (mobile toy car) and auditory (air blast) stimuli. Cortisol levels decreased back to the baseline after the second challenge. The behavioral observations showed that these MWD were more active, and presented less stereotypic behaviors (pacing, manipulation of the environment) during both visual challenges, whereas half low posture was observed during the first but not during the second visual challenge. The present study shows that this group of MWD still has an adaptation capacity to an environmental challenge (return to baseline of the cortisol levels, a higher posture during the second than at the first challenge). These results are encouraging and indicate that the dogs might have a diminished welfare (i.e. stereotypic behaviors), but are not chronically stressed.