The contractual working relationship between the contractor and the assignor in implementing a project is very complex. So that in achieving the success of the project, a project implementation system with integrated delivery and effective communication between organizations is needed. This study aims to analyze project success in terms of integrated project delivery and communication between contractors and task givers. The independent variables used in this study are integrated project delivery (x1) and communication (x2). The dependent variable used is project success (y). The samples in this study were 42 respondents. Data were collected by distributing questionnaires. The collected data were analyzed using structural equation modeling (SEM) with validity, reliability and hypothesis testing. The results showed that the implementation of integrated project delivery and communication had a positive and significant effect on the success of the project between the contractor and the assignor. Meanwhile, influential indicators are: innovative project delivery system (x1.20) and the coordination relationship between the project office and the head office (x2.15). Keywords: Integrated project delivery, Komunikasi, Kontraktor, Owner, Keberhasilan Proyek.