<p>People who are marginalised in slum-upgrading processes can benefit from participatory design strategies. When marginalised slum communities confront and explore conflicting perspectives, values, assumptions and goals through negotiation within participatory design processes, the ability to harness the collective intelligence of people to work towards collective action can be enhanced. However, a tension exists in the participatory design literature between those participatory processes that seek to facilitate social outcomes such as social capital building, and those that seek only to implement an urban development or upgrading project (slum upgrading) as the outcome. Exploring new methods of design participation that integrate both social outcomes and design processes can help alleviate this tension by recognising a diversity of stakeholder perspectives on urban-related issues and help them work towards implementing lasting communal change that explicitly takes into account cooperative development action. The dissertation explores an innovative approach to participatory slum upgrading, which proposes bringing together speculative architecture, participatory design, and serious gaming approaches to help stakeholders to explore conflicting perspectives, assumptions and corresponding future visions surrounding architectural and urban issues. The research focusses on how these three areas can be brought together to help develop a new approach for designing participatory design tools for marginalised communities. The research explores how a “speculative, participatory, serious urban gaming” (SPS-UG) approach might be used to help marginalised communities consider past, future and present community experiences, reconcile dissimilar assumptions, and generate social outcomes and in-game design responses, while priming participants for further long-term, slum-upgrading design engagement processes. Empirical material for this research was gathered from a range of case study workshops prepared with three landfill-based communities and external partners throughout 2017, which utilised a new SPS-UG computer game I designed called Maslow’s Palace to evaluate the approach. The research shows that the SPS-UG approach was successful in guiding the design of a serious game to help reveal, develop and ground stakeholder knowledge, goals and values surrounding slum-upgrading issues. Through an exploration of social complexities involved in the participatory design process, participants were stimulated to share diverse opinions and aspirations and thus deepen their understanding of self, others, norms and institutions. The SPS-UG approach contributed to slum-upgrading outcomes for communities by aiding slum-upgrading ideation, framing the consideration of alternate views and possible futures, and scaffolding discussions about what the future might look like through visual representation of possible design alternatives. Finally, the research discusses key methodological insights, and the challenges faced when working with marginalised communities while pursuing social and slum-upgrading outcomes through a gaming approach. This is significant when considering how the approach might interface with other slum-upgrading processes outside of the scope of this research or function as a catalyst for the transformation of other physical urban environments and socio-cultural contexts.</p>