Caring for an offspring diagnosed with a psychological chronic disorder is used in research as a model of chronic stress. Indeed, it is usually associated with disturbances in the salivary cortisol (Csal) levels of the caregiver. An imbalance between salivary testosterone (Tsal) and Csal levels is a marker of proneness to social aggression. Given this, we aimed to establish whether the salivary testosterone/cortisol (Tsal/Csal) ratio response to acute stress could be employed as a marker of proneness to anger in informal caregivers of offspring with autism spectrum (ASD). Tsal/Csal ratio and anger responses to a set of different cognitive tasks as well as anger trait and expression were compared in these informal caregivers and controls. Caregivers, particularly those of offspring with ASD, had higher Tsal/Csal ratios than controls in response to acute stress, concretely after the stress in the case of fathers (p = .05) and before stress when analyzing mothers (p = .05). Moreover, ASD fathers and mothers obtained higher magnitude of the T/C ratio response to stress (p = .03 and p =.04, respectively), anger state (p = .02 and p = .02, respectively) and expression scores (p = .05 and p = .05, respectively) than controls. Finally, high Tsal/Csal ratio levels and response to stress were significantly associated with high anger feelings increases (p < .01 and p < .001, respectively), trait (p < .001 and p > .05, respectively) and expression (p < .05 and p > .05, respectively) in caregivers.