PURPOSE: This study is a process evaluation of the use of Individual Placement and Support (IPS) and Participatory Workplace Intervention (PWI) to increase the work participation of people with work disabilities. We ran the evaluation alongside a randomized controlled trial (RCT), to investigate whether and to what extent IPS and PWI were executed according to protocol. METHODS: The study population consisted of clients with work disabilities, and their job coaches who were employed by the municipality of a large city in the Netherlands. Data were collected between September 2019 and November 2022 using registration forms, accompanied by researchers' notes and logbooks. RESULTS: For IPS the dose delivered was reasonable and the IPS fidelity measurement score was fair. The job search focused on paid work for almost all clients and was based on their wishes as indicated in the protocol, but integration of employment services with (health) care was often lacking. A minority of the clients who were assigned to PWI received the intervention, often because the client did not start work within the follow-up period and a workplace was a requirement to apply the intervention. CONCLUSION: The results of this study show that IPS was executed reasonably and with a fair fidelity, which indicated implementation was sufficient to find an effect on work participation in the RCT. PWI was barely realized in practice and no conclusions regarding the fidelity could be drawn. We therefore conclude that we cannot expect PWI to have any effect on work participation in the RCT.