This chapter summarizes the scientific foundation for career and workforce development interventions with the intent of providing insight into what constitutes evidence-based career interventions. Spokane and Oliver (1983) defined “vocational interventions” as any treatment or effort intended to enhance an individual’s career development or to enable the person to make better career-related decisions. We have a similar definition of career and workforce development interventions, which is any treatment or effort intended to enhance an individual’s career, occupational, or work-related development, or to enable the person to make better work-related decisions and help the individual to manage work transitions. This is a broad definition that encompasses a wide array of interventions, such as individual counseling, group activities, career classes, computer information systems, and self-help interventions.