There is a lack of knowledge regarding real-time emotional reactivity to high-intensity stressors, particularly in people with mental illness, a potentially vulnerable population. The current study aimed to examine negative emotional reactions to recurring high-intensity stressors within a continuous war situation, in people with different psychiatric diagnosis types. Experience sampling method was used to examine emotional reactions among 143 civilians exposed to rockets during the 2014 Israel-Gaza war, of them 18.2% with psychosis, 14.7% with anxiety or depression and 67.1% without mental illness. Participants reported exposure to rocket warning sirens and the levels of ten negative emotions twice a day for 30 days. Negative emotional levels were higher on most emotions following high-intensity stressors (sirens), i.e., emotional reactivity was demonstrated in real-time during war. Overall, no difference in reactivity was found among the three study groups. Moreover, people with anxiety/depression were less reactive than people without mental illness on sadness and being overwhelmed. The findings indicate similar and sometimes lower emotional reactivity to high-intensity stressors in people with mental illness compared to the general population. Nevertheless, people with mental illness seem to have significant emotional needs during war, to be addressed in prevention and intervention efforts. This article is protected by copyright. All rights reserved.This article is protected by copyright. All rights reserved.