Background: A majority of patients with psychosis have experienced trauma, but trauma-focused (TF) treatment is not routinely offered. As new studies are published continuously, updated reviews are necessary to guide clinical practice, including a broader focus on several outcome variables. The current systematic review set out to examine the effect of TF treatments in patients with a psychotic disorder and comorbid trauma symptoms on symptoms of (1) trauma, (2) psychosis and (3) anxiety, depression, and psychosocial functioning. Methods: A systematic search following the PRISMA guideline yielded 17 studies reported in 19 records, which were evaluated and presented. Results: Overall, results indicated positive effects on trauma symptoms following TF Cognitive Behavioural Therapy, Eye Movement Desensitisation Reprocessing, Prolonged Exposure, Written Emotional Disclosure, and Imagery Rescripting. Results were inconclusive but suggestive of positive effects for other outcomes. Discussion: The present findings gives preliminary support for the effect of TF treatment on trauma symptoms, but are more inconclusive for outcomes related to symptoms of psychosis, anxiety, depression, and psychosocial functioning. In addition, support was found for treatments delivered both individually and by group. The current evidence base on TF treatment in psychosis is, however, still at an early stage and challenged by methodological issues.