Buildings are known to significantly affect the global carbon emissions throughout their life cycle. To mitigate carbon emissions, investigation of the current performance of buildings with regard to energy consumption and carbon emissions is necessary. This paper presents a process-based life cycle assessment methodology for assessing carbon emissions of buildings, using a multi-storey reinforced concrete building in a Sri Lankan university as a case study. The entire cradle-to-grave building life cycle was assessed and the life span of the building was assumed as 50 years. The results provide evidence of the significance of operation and material production stages, which contributed to the total carbon emissions by 63.22% and 31.59% respectively. Between them, the main structural materials, concrete and reinforcement steel made up 61.91% of the total carbon emitted at the material production stage. The life cycle carbon emissions of the building were found to be 31.81 kg·m-2 CO2 per year, which is comparable with the values obtained in similar studies found in the literature. In minimizing the life cycle carbon emissions, the importance of identifying control measures for both building operation and material production at the early design stage were emphasized. Although the other life cycle stages only contributed to about 5.19% of the life cycle carbon emissions, they should also receive attention when formulating control strategies. Some of the recommended strategies are introducing energy efficiency measures in building design and operation, using renewable energy for building operation and manufacturing of materials, identifying designs that can save mass material quantities, using alternative materials that are locally available in Sri Lanka and implementing material reuse and recycling. This study is one of the first to undertake a life cycle carbon emissions assessment for a building in the Sri Lankan context, with the hope of facilitating environmentally-friendly buildings and promoting sustainable construction practices in the country.