The public sector, for various reasons — including shortages in development budgets — welcomes private-sector investment in projects. One such approach is the Build–Operate–Transfer (BOT) method. Previous models indicate that, in each of these projects, the variables “public/private sector characteristics, joint decision-making, trust, commitment, members’ belief in the benefits of collaboration, and process/structure” act as factors influencing the phenomenon of collaboration; likewise, a desirable level of collaboration gives rise to outcomes such as “efficiency, innovation, satisfaction, benefits, and willingness for future investment”. The aim of this research is to examine the relationships among these variables and to identify the factors with a greater effect on the outcomes of collaboration in Build–Operate–Transfer projects. The research method was survey-based and quantitative; the research instrument was a researcher-made questionnaire; and the analysis was conducted using regression in SPSS. To this end, using documentary and survey methods with a quantitative approach, and after collecting data based on the opinions of experts in this field, the data were analyzed using regression testing and SPSS software. The results of the research showed that the initially proposed model was confirmed, and that the factors affecting collaboration have an effect on the outcomes of collaboration. Among the variables of the influencing factors, “process/structure” was the most important variable affecting the outcomes of collaboration, and it had a particularly significant effect on “benefits” and “willingness for future investment”. Also, the variable “members’ belief in the benefits of collaboration” affected “innovation” and “satisfaction”, and the variable “private-sector characteristics” had an effect on “efficiency”. The coefficients of determination obtained ranged from 7.7% to 32.3%, and focusing on improving “process/structure” had the greatest effect on “benefits” and “willingness for future investment”. The main novelty of the present research is the quantitative examination of these relationships for the first time.