Cognitive impairment occurs across several neuropsychiatric diseases and impede everyday functioning and quality of life. Fully immersive Virtual Reality (VR) aid motivation and engagement and therefore has a potential to help overcome the obstacles in the field of cognitive rehabilitation. The aim of this systematic review is to investigate whether VR can be a useful intervention in cognitive rehabilitation transdiagnostically. We identified nine studies with randomized controlled trials following the PRISMA guidelines in databases Pubmed, Embase and PsychInfo. The trials were all evaluated through Cochrane Collaboration's Risk of Bias. The studies were conducted in patients with mild cognitive impairment (k=4), schizophrenia (k=3), ADHD (k=1), or stroke (k=1) and involved 6-12 weeks of training. Overall, results showed improvement in some domains of cognition, primarily executive function and attention. The studies were pilot studies with 6-34 participants per treatment group. Risk of bias was either high (k=3) or moderate (some concerns) (k=6). Key reasons were suboptimal statistical analyses and lack of clarification on randomization and blinding of participants and assessors. In conclusion, this review found promising evidence for VR cognitive rehabilitation for neuropsychiatric illnesses. However, larger and methodologically stronger studies are warranted to establish the full potential of VR.