Building Information Modeling (BIM) is the comprehensive process of developing a computer model of a building project in the phases of designing, analyzing, building, managing, refurbishing and even demolishing the building. Applying BIM to public construction has become an obligation in South Korea. According to the Public Procurement Service in South Korea, the use of BIM has been compulsory on all government projects over $44M since 2012. Moreover, from 2013, the application of BIM will be expanded to all public construction projects over $27.6M. Finally, beginning in 2016, all public construction projects will be required to use BIM. Most research on BIM in South Korea has been focused on developing regulations and policies, application of BIM, solving technical problems, and searching for the value of BIM. However, the use of BIM in Korea during construction for decision-making has not been thoroughly reported in Korea yet. One may be wondering then if BIM is indeed well utilized in Korea during construction for practical decision-making. The objective of this research centers on investigating how a construction company in South Korea is using BIM for its decision making process during ongoing construction phases. For this investigation, a case study method was used. The construction operations on a jobsite in South Korea were monitored June to August in 2012. Field notes were taken to document the decision-making process and information used during field coordination meetings. A total of 36 cases were monitored and recorded. The use of BIM on field was then compared to the industry expectations indicated in the literature. Specifically, the use of BIM for scheduling, estimating, coordination, review of drawings, and tracking for change orders were carefully monitored and compared with the industry expectations as they were addressed in the literature. The results of this research study were mixed. That is, there are not only similarities, but also differences between BIM’s role used for decision making at the construction site, and its expected role described in previous research. The similarities were regarded as minimizing reworking. This factor came to fruition at a construction site by minimizing error, omission in design phases, or congruence in design and construction tasks. These factors could have a positive effect on estimating and scheduling at a construction site. However, use of BIM at a construction site was still limited in reducing repetitive work when 2D drawings were not able to provide enough information to conduct construction. Additionally, even though this study was successful in revealing the connection between the decision making process and the application of BIM at a construction site, the results of the study may not be generalizable to the construction industry as a whole in South Korea. Therefore, further research is needed to ensure its applicability to other construction projects.