Background: Transcranial random noise stimulation (tRNS) is a non-invasive brain stimulation technique that modulates cortical excitability through stochastic resonance. While promising, its safety and efficacy in psychiatric disorders remain underexplored. Objective: To systematically evaluate the efficacy and safety of tRNS in various psychiatric disorders. Methods: A systematic review was conducted per PRISMA guidelines and registered on PROSPERO (CRD420251040192).Databases searched included CENTRAL-Cochrane Central Register of Controlled Trials, PubMed, Scopus, and Web of Science. Studies were included from their inception to 30th April, 2025. Studies involving tRNS in psychiatric populations, regardless of study design, were included. The risk of bias was assessed using JBI tools. Results: 22 studies were included (642 individuals), spanning ADHD, depression, schizophrenia, dyslexia, and other conditions. Most studies used 20-minute tRNS sessions over 1−4 weeks. ADHD and dyslexia showed consistent improvements in overall executive function and reading & phonological skills, respectively. Schizophrenia studies demonstrated significant reductions in negative symptoms and auditory hallucinations. Effects in depression were mixed, with some studies reporting substantial symptom relief, while others found no significant benefit. Across disorders, tRNS was generally well-tolerated with only mild, transient adverse effects. Conclusion tRNS appears to be a safe, well-tolerated, and potentially effective intervention for specific psychiatric symptoms, especially in ADHD, dyslexia, and schizophrenia. However, inconsistent protocols and mixed outcomes in mood disorders highlight the need for standardized protocols and further research.