The high-rate urbanization in Addis Ababa has augmented the need to develop sustainable land use and this has influenced the policymakers and planners to look to the underground space as a new frontier to urban expansion. This paper measures sustainable urban planning strategies that can be used to develop and use underground space in Addis Ababa with a focus on environmental resiliency, land-use efficiency, infrastructure efficiency, and urban sustainability in the long-term. Based on a multi-method research design that involves literature synthesis, spatial planning evaluation, policy analysis, and expert interviews, this study will determine the major limitations, opportunities and sustainability indicators that affect development of underground space in the city. Findings point to the fact that the model of surface-based urban development of Addis Ababa is progressively becoming inefficient as the topography constrains it, informal developments spread, traffic congestion intensifies, and the pressure on green spaces grows. The study concludes that implementation of underground space planning including transit hubs, utility tunnels, commercial facilities and stormwater systems can greatly decrease land use, improve mobility and increase resiliency of the environment under the condition of their integrated planning. Results also indicate that geology of the urban area, engineering feasibility, regulatory preparedness, energy-use trends and social economic acceptance influence sustainability in underground development. Through a detailed analysis, the paper presents a sustainability-based model of planning to be applied to Addis Ababa that will involve environmental assessment, underground zoning, risk-reduction, and intersectoral coordination. The article finds that the development of sustainable underground space can also be a viable and strategic way of solving the spatial and environmental problems of Addis Ababa as long as policy and governance system as well as technical capacity gaps are mitigated. Some of the suggestions involve underground master planning, broad geotechnical mapping, legal frameworks and interdisciplinary collaboration in future urban resilience.