The aim of the article is to determine the conditions for the effective use of group psychotherapy in working with servicemen with post-traumatic stress disorder (PTSD). The research employed the methods of testing and formative experiment. The sample consisted of the servicemen with PTSD symptoms. The group psychotherapy programme demonstrated uneven effectiveness. The effectiveness of individual and group work in reducing the symptoms of re-experiencing the event is moderate. Manifestations of avoiding traumatic situations did not change significantly in the process of group influence, while a moderate positive influence was recorded in the case of applying an individual approach. Group psychotherapy is the most effective in working with symptoms of emotional arousal of servicemen, which results from trauma. The significance of the implementation of the obtained results lies in the development of effective programmes and protocols of psychotherapy aimed at overcoming post-traumatic stress disorder of veterans and combatants. Further research may focus on expanding the research sample and the implementation of an experimental combination of individual and group psychotherapy in the work with servicemen with PTSD.