Growing concerns over the importance of reducing the embodied carbon (EC) of buildings have led to a greater focus on EC-related research and policymaking. Nevertheless, the Sri Lankan building sector is currently lagging behind on this issue. While a few studies have been conducted on the EC impacts of different buildings, further research is needed on impact estimation in order to inform policies and guidelines on EC reduction, with assessment or estimation being the main driver towards reduction. Thus, this study aims to present, evaluate, and discuss EC assessment methodology and the assessment results drawn from twenty case studies in Sri Lanka, including low-, medium-, and high-rise office buildings. The results indicated that the EC extent of buildings ranged between 384.45 and 677.39 kgCO2e/m2. The average EC extent of each building category was valued at 522.18 kgCO2e/m2 (low-rise buildings), 457.85 kgCO2e/m2 (medium rise), and 567.51kgCO2e/m2 (high-rise). Irrespective of the building category, the substructure, frame, upper floors, and external walls were identified as the carbon critical elements, accounting for about 85–95% of overall EC. Internal walls and partitions, stairs and ramps, and roof elements were insignificant carbon elements, contributing less than 20% of EC. This study further revealed some practical indications on optimal EC reduction strategies for office buildings. Importantly, the overall work provided quantitative information that enables the decision-makers to make decisions on reducing EC of buildings in Sri Lanka.