Objective: Skill building for adults involves multiple approaches to address the complex problems related to serious mental illness. Individuals with schizophrenia are often the research focus. The authors outline key skillbuilding approaches and describe their evidence base. Methods: Authors searched meta-analyses, research reviews, and individual studies from 1995 through March 2013. Databases surveyed were PubMed, PsycINFO, Applied Social Sciences Index and Abstracts, Sociological Abstracts, Social Services Abstracts, Published International Literature on Traumatic Stress, ERIC, and CINAHL. Authors chose from three levels of evidence (high, moderate, and low) on the basis of benchmarks for the number of studies and quality of their methodology. They also described the evidence of service effectiveness. Results: Over 100 randomized controlled trials and numerous quasi-experimental studies support rating the level of evidence as high. Outcomes indicate strong effectiveness for social skills training, social cognitive training, and cognitive remediation, especially if these interventions are delivered through integrated approaches, such as Integrated Psychological Therapy. Results are somewhat mixed for life skills training (when studied alone) and cognitive-behavioral approaches. The complexities of schizophrenia and other serious mental illnesses call for individually tailored, multimodal skill-building approaches in combination with other treatments. Conclusions: Skill building should be a foundation for rehabilitation services covered by comprehensive benefit plans that attend to the need for service packages with multiple components delivered in various combinations. Further research should demonstrate more conclusively the long-term effectiveness of skill building in real-life situations, alone and in various treatment combinations. Studies of diverse subpopulations are also needed. (Psychiatric Services 65:727-738, 2014; doi: 10.1176/appi.ps.201300251) D eveloping or regaining basic skills needed to function adaptively in real-world situations is essential for individuals who are struggling with serious mental illness, substance use disorders, or co-occurring mental and substance use disorders. The neurodevelopmental nature of certain severe mental illnesses (1)-in which multiple and complex skill deficits emerge early in development, persist through adulthood in the absence of targeted treatment, and affect virtually every aspect of life functioning-has led to a vast array of approaches to skill building. These approaches are typically applied in various combinations.The inherent complexity of skill building adds a high degree of challenge to assessing levels of evidence and effectiveness for such a diverse array of treatment modalities and methods. In this review, we examined four key components of skill building: social skills training (including life skills training), social cognitive training, cognitive remediation, and cognitivebehavioral therapies that target skills for coping with psychotic pr...