A teacher, who has a major role in the formation of class culture, needs to have proficiencies to design effective learning environments. The reflection of these proficiencies on classroom practices takes place via the decisions taken under critical situations. This study aims to find out the components underlying teachers' decision-making Participants of the study which was designed as a case study were elementary school mathematics teachers. The study was carried out through the individual interviews with participants about the decision making under critical situations after analysing participant teachers' course observations which were video-recorded by the researchers. Data obtained from the interviews were analysed through content-analysis method. Based on the findings, it was found that teachers' professional proficiencies could be presented in the same frame with the variables reflected on decision making.