In this thesis, the value of design is researched within the context of municipalities and how civil servants deal with complex problems. Loneliness amongst adolescents is a complex problem that many are not aware of yet. Of the youth between 12 and 18 years old in Delft, 42% states to feel lonely (GGD Haaglanden, 2016). This issue needs to be addressed by Team Youth of Gemeente Delft. However, the civil servants and their partners do not act upon it. This led to the following research question of this project: “Will a design-led approach enable the civil servants of Team Youth from Gemeente Delft to act upon the complex problem of loneliness amongst adolescents in Delft together with other relevant actors?” First, three sub-questions were posed to find out what the design-led approach should consist of. They were answered through literature and field research. The first question addressed systemic design and showed that such an approach allows different actors to collaborate to find a mutual understanding of a situation. This enables the actors to create and follow a shared vision, for which interventions can be developed. The second sub-question gave insight into the current situation of loneliness amongst adolescents in Delft. A causal system map was created, which revealed six interconnected root causes that give a subjective explanation of why the problem is as it is. When researching why Team Youth currently does not act upon this situation, it was found that the policy implementation process is not performed optimally. This process was researched, and four areas of improvement were found. The involvement of unvaried parties, a consultative role of the civil servant, a conventional approach and an undefined structure of the process counteract when dealing with complexity. The third sub-question concerned the research of design principles that might improve or enrich these four areas. Co-design was discussed, which demands a collaborative role and the use of participatory techniques. To create one structured process that focuses on dealing with complexity and creating mutual understanding, the Systemic Design Toolkit process was mentioned. The insights and design principles from the research were translated into requirements for the design-led approach that would be set up. A research through design process followed, in which a systemic co-design process with four phases was set up, performed and researched. First, a network and co-creation team was built. Next, two co-creation sessions took place to explore the problem field and solution space. In the last phase, the results were discussed with Team Youth, which led to a defined action for the policy implementation plan. With the insights and results from the process, and help from actors in the network, the assigned actor was able to enact the action and develop an intervention. The research and evaluation of the performed process resulted in an adjusted list of requirements on which the final proposal is based: the WIJ-model (Welzijn Implementatie Jeugd model). This systemic co-design process enables civil servants to act upon complex problems during the policy implementation phase and implement well-being amongst the youth of Delft.