Despite the progress in recent decades, one in ten people globally still live in extreme poverty, and this number is set to increase in the coming years. Designing interventions to improve well-being and livelihoods is challenging because poverty is multidimensional and plays out in complex, adaptive social-ecological systems, where behaviours and practices at the local level can have unintended consequences elsewhere in the system. In such contexts, linear approaches to designing development interventions are insufficient. Service design has emerged as a human-centred, integrative approach to designing services and systems in complex settings, but knowledge gaps remain on how service design can be used to address development challenges in the Global South. Without an understanding of how service design tools and approaches function in these contexts, there is a risk they might inadvertently cause harm to research participants and local communities. This thesis contributes new knowledge about how service design can be used to design development interventions in complex social-ecological contexts The research questions address three areas where service design could play a role: (i) how service design could be used to make sense of local level complexity and package this information for development programmers and policymakers; (ii) how service design could support local agency in the design of development projects; and (iii) how service design could be used to complement conventional methods of development research.The research questions were addressed using three case studies of development interventions. In two of the cases, a clean cookstove intervention in Kenya and an insurance product for small-scale farmers in Uganda, a service design approach was combined with quantitative methods. In the third case study, participatory backcasting was used to inform a long-term plan for energy transition for an off-grid community in Machakos, Kenya. A conceptual framework was first developed to support the use of service design to address development challenges in complex social-ecological systems. Elements of the framework were then applied in two of the case studies: the cookstoves and insurance studies. The thesis uses service design as an approach and practice, and the capabilities approach as the main conceptual and theoretical framing.I would like to thank my supervisors, Stefan Holmlid and Matthew Osborne. Stefan, thanks for agreeing to take me on and for being as curious as me about the role of service design in development settings. You embody the design research attitude-keeping inquiries open and experimental, rather than narrowing the focus. Although at times frustrating, this approach has broadened my horizons and made me a better thinker. To Matthew, my friend and co-pilot these past six years. Thanks for being at once rigorous and creative, and for taking a chance on these service design methods, and on me. Your clear and honest feedback helped me see the wood for the trees writing the kappa, and your sense...