There is growing interest in Life Cycle Assessment (LCA) of buildings, as it is a robust tool for evaluating environmental impacts across a building’s lifespan. Office fit-outs are a critical yet often overlooked component in LCA studies, involving the frequent replacement of interior elements like finishes, fixtures, furniture, and services due to lease terms and contractual obligations. The recurring fit-outs account for considerable material consumption and waste. This research addresses the knowledge gap by investigating the potential of office fit-outs in reducing carbon emissions. LCA studies of four Green Star Interiors-certified office fit-outs in Australia were conducted to assess their whole-of-life carbon impacts. A cross-case analysis was used to identify effective low-carbon strategies and common challenges in conducting LCA for fit-outs. Findings revealed that retaining existing finishes and reusing selected equipment and furniture offer the greatest potential for embodied carbon reduction while further reductions came from careful material selection, particularly through low-carbon alternatives. Operational carbon can be diminished through improvements in the efficiency of building services, including lighting, HVAC, IT system and appliances. Adopting sustainable fit-out strategies can reduce whole-of-life carbon emissions by up to 33% (5% savings from embodied carbon and 28% from operational carbon) compared to a business-as-usual case with no sustainability interventions. Challenges and considerations in LCA modelling included defining fit-out scope and system boundaries, modelling technique of material reuse, data availability, and interpreting Environmental Product Declarations (EPDs). These factors influenced the accuracy and comparability of LCA results across projects. Overall, the results shed a new light into the understanding of whole-of-life carbon emissions of fit-out projects and demonstrates how comprehensive LCA studies can effectively inform design decisions. The study provides practical insights to improve fit-out practices and support the transition towards more circular and sustainable approaches in the built environment.