This thesis ‘Towards sustainable projects´ will focus on the integration of sustainability aspects in projects in the engineering industry. This research uses the following definition for ‘sustainability’: “meeting the needs of the present without compromising the ability of future generations to meet their own needs” (Brundtland, 1987). This means that in this research ‘sustainability’ is about aspects which ensure that a population’s present and future needs can be met. These are in essence relevant variables within the three ‘topics’ within sustainability: environmental, economic and societal aspects. The integration of sustainability within engineering projects is still limited. Regulation and tools give guidance on integrating sustainability aspects, for example BREEAM and the Sustainable Development Goals, however, these seems to be more of an exception rather than a rule. Even though projects are part of a bigger system, they can influence the part they are involved in. As Robert Swan quotes (2012): "The greatest threat to our planet is the belief that someone else will save it.” The role of project managers is to steer their projects. Project manager are the connecting link between the client and the engineers, and from this position they can influence both parties to incorporate sustainability in their projects. It is unclear what influences the incorporation of sustainability in projects, so the following main research question needs to be answered: What influences the integration of sustainability in engineering projects? In order to answer this main research question, three research steps were taken. Firstly, the most relevant sustainability aspects within projects were collected from Sustainable Impact Assessments (SIAs) from literature. Thirty aspects were selected as most important for sustainable projects as these were mentioned most in all SIAs. The thirty aspects consist of: eleven aspects about the environment, for example minimising CO2 emissions or minimise the amount of waste; eleven aspects about society, for example development of human capital or respecting human rights; and eight aspects about economy, for example procurement and business agility. Secondly, a group of 20 Dutch project managers of Royal HaskoningDHV with various types of projects within the engineering industry ranked the thirty sustainability aspects based how difficult it was to integrate the sustainability aspects in their project. It was determined that the aspects about people were most easy to integrate, meaning ‘health & safety’, ‘ethical behaviour’, ‘fair and safe labour’ and ‘human rights’. On the other hand, the most difficult aspects to integrate were the aspects about planet, meaning ‘transport’, ‘CO2 emissions, ‘harmful emissions’ and ‘material efficiency’. Thirdly, the participants were asked to give motivations for ranking the five most easy and most difficult sustainability aspects to integrate in projects, as they have during the second step. It was expected that project characteristics as the type of project, the type of client and the project size would influence the ease of integrating sustainability aspects in projects. Results show that the integration is influenced more by the personal motivation of the client, the project manager or the company strategy and vision, rather than by the project’s characteristics. This is shown in the interviews and because there is no direct link between the sustainability aspects and the project’s characteristics. In order to answer the main research question, the most influencing reasons can be divided into five groups: process, product, supplier, client and society.