The Iraqi construction industry suffers from many issues that lead to many design errors, clashes, delays and cost overruns. Therefore, applying constructability will prevent these issues from happening, as it has proven its positive effect in different projects around the world. The goal of this paper is to use building information modelling (BIM) to assess the constructability, provide the opportunities for the project stakeholders to choose the best constructable design alternative and find the affection of applying constructability on project cost. The practical side of this research consists of two parts: in the first part, 37 factors are collected from the literature review as factors that effect on constructability. After that, a survey occurs in two sessions an open and closed questionnaire. The results were analyzed, and their mean, standard deviation, Cronbach's Alpha and developed weight will be found. The second part clears the method of linking these factors with BIM in order to assess the constructability in two different designs’ projects and find their cost. The method applies through a case study of an educational building located in Baghdad, Iraq; Rivet and Microsoft Excel programs are used in this paper. the result approves the success of using BIM technology to assess the constructability of a project in Iraq. Also, it shows how project cost will be affected when applying constructability factors.