Competitive employment contributes to the health and recovery of individuals with severe mental illness (SMI). However, employment rates among these individuals are low, often leading them to rely on social assistance or disability benefits. Individual Placement and Support (IPS) is an evidence-based, effective, and cost-effective approach for helping individuals with SMI obtain and maintain competitive employment. Despite its effectiveness and cost-effectiveness, the implementation of this approach has been challenging worldwide. Inadequate funding and insufficient collaboration between mental healthcare and vocational rehabilitation services are major barriers to implement IPS within usual mental healthcare. To improve the implementation of IPS in the Netherlands, the Dutch Social Security Institute: the Institute for Employee Benefits Schemes (UWV), began offering nationwide reimbursement for IPS in 2012 to all mental healthcare agencies providing IPS services. Multiple health insurance companies also contributed by funding the intake phase of IPS trajectories. In addition, various national collaborations among stakeholders in mental healthcare and vocational rehabilitation were initiated. An example of such an initiative involved stakeholders from two mental healthcare agencies, UWV, a municipality, and a health insurance company. This collaboration included a multifaceted implementation strategy (MIS) for IPS, encompassing an organizational and a financial component. The organizational component comprised regular meetings at two levels among the professionals of the different organizations involved (i.e., two mental healthcare agencies, UWV, a municipality and a health insurance company): 1) at the management level, there were regular meetings among decision makers who had a managing or advising role within their organization. Their main goal was to facilitate involved practitioners and to ensure IPS sustainment; 2) at the practitioner level, there were regular meetings among IPS employment specialists and several vocational rehabilitation professionals (i.e., the labor expert and insurance physician from UWV, and the case manager from the municipality). Their main goal was to organize the IPS funding for new clients, and to provide improved benefits counselling as compared to usual IPS practice. The financial component consisted of secured IPS funding with a ‘pay for performance’ element, providing mental health agencies with extra payments for successfully placing IPS participants in competitive jobs. The research in this thesis primarily focuses on IPS using a multifaceted implementation strategy (IPS+MIS). The objectives of this thesis are: 1) to gain insight into the implementation of IPS, the employment outcomes of IPS participants with SMI, and the factors that influence these employment outcomes; and 2) to evaluate the effectiveness and cost-effectiveness of IPS implemented through a reimbursement strategy on a nationwide scale, in terms of achieving sustainable, competitive employment. By addressing these objectives, this thesis aims to contribute to improving employment outcomes for individuals with SMI by assisting stakeholders in making better-informed decisions regarding the implementation, funding, and organization of IPS. In conclusion, the results of this thesis show that IPS implemented through a reimbursement strategy on a nationwide scale is effective and seems cost-effective in individuals with SMI. The results also indicate that the organizational implementation strategy has positively impacted the implementation of IPS within usual mental healthcare. However, significant efforts are still required to address the remaining barriers at the socio-political level as highlighted in this thesis and to further improve both the implementation of IPS and the work participation of individuals with SMI. Other barriers can be addressed by intensifying collaboration between mental healthcare clinicians and social medicine specialists, and by increasing the involvement of these specialists within IPS services.