Background: Working in a project setting has been common since the nineteenth-century and has been developed in numerous industries until today. Nevertheless, we have found a gap in research, to separately study managers’ and leaders’ way to influence the success in projects. We believe that to study how the functions of managers and leaders affect the outcome of a project, will bring new knowledge for how the people involved in a project can create a successful project. This is important and interesting to be aware of due to the increasing working method nowadays, which is to work in projects. With more knowledge for what act that affect a successful project, the easier it will be for the manager and/or leader involved in a project to reach the set of objectives for the project and then create a successful outcome. Problem: Since working in the form of projects is a common method today, it is interesting to see which functions of the project manager that is most important to develop, to be able to reach the objectives of a project. This can be measured by using The Iron Triangle, and by that evaluate how the functions of managers and leaders, explained by Kotter, influence project success. Kotter’s functions of managers and leaders are until today only applied in the context of organizations; therefore we want to see how these might influence in a project situation. Purpose: The purpose of this thesis is to see how Kotter’s functions of managers and leaders influence the objectives for a project, using the criteria in The Iron Triangle for measuring project success. Method: The thesis is based on face-to-face interviews with three project managers. The interviews were divided into two parts; the first part with opened questions and the second part with closed questions. The empirical findings have been analyzed with the theories from the frame of reference as a foundation. By doing so, the theories have been challenged to as well as strengthened to the findings based on the interview material. Conclusion: Based on the findings from the interviews with the projects managers, we can conclude that the theory presented in the frame of reference; Kotter’s functions of managers and leaders in combination with the The Iron Triangle, are not completely relevant in all situations when measuring the success of a project. All functions of Kotter are not required and all criteria in The Iron Triangle are not important for measuring the success. Additional finding was that one essential part for the project success was that the objective for a project should be set and clearly spelled out in advance to the people involved in order to create a successful outcome.