Psychotic disorders are a group of severe mental disorders which affects 2-3% of the population and constitutes one of the leading causes of disability worldwide. Early intervention (EI) represents a major paradigm shift in psychiatric service and has been demonstrated to be effective in outcome improvement for first-episode psychosis (FEP) and at-risk mental state (ARMS). However, despite the promising findings, evidence has shown that a significant proportion of early psychosis patients still experience suboptimal clinical outcomes (such as high relapse risk, partial remission, early-onset treatment resistance, persistent negative symptoms, etc.), functional impairment and cognitive dysfunction. Further research clarifying the complex inter-relationships among symptomatology, psychosocial functioning, and cognitive deficits in the early illness course as well as evaluating effects of EI on further improvement on clinical, functional, and cognitive outcomes in patients with early psychosis would therefore facilitate development of next-generation EI service to enhance short-term treatment outcomes and long-term prognosis. This Research Topic aims to further our understanding of the complex relationships between symptomatology, psychosocial functioning and cognitive impairment in the early course of psychotic disorders, including first-episode psychosis (FEP) and at-risk mental state and to evaluate the effects of early intervention, either in terms of specific treatment modalities or in the comprehensive service framework, on further improvement in clinical, functional, and cognitive outcomes in patients with early psychosis.