Education is usually organized along the line of mono-disciplines. It is however argued that a focus on solving problems, designing and advising for clients will be more meaningful for students and will enhance their motivation for Science, Technology, Engineering and Mathematics subjects and careers. Therefore, the Dutch network of Technasia schools have positioned Integrative STEAM projects for clients central in their curriculum. Usually these projects are related to one discipline and conducted by students with a science-oriented profile. In a pilot, 8 schools developed and conducted Multidisciplinary STEAM Projects for pupils in grade 9 to 11 using social cooperative approaches such Jigsaw and perspective-based question prompts that scaffold multi-disciplinary ways of thinking. The self-determination theory links intrinsic motivation with the presence of autonomy, relatedness, perceived competences. The theory also links the way students perceive the relevance of their learning activities to motivation. Therefore the Intrinsic Motivation Inventory (IMI) questionnaire was used to determine half-way and after the project of 182 students their interest and enjoyment as well perceived competence, effort, pressure, perceived choice, value/usefulness and relatedness. For relatedness to peers and to the client the original statements from IMI were adapted. The results show that intrinsic motivation was slightly positive on average, while relatedness between teammates was positive and pressure low. Students experienced working from different disciplines as valuable. It is suggested to develop new items to measure relatedness to the client as those based on the original IMI where not able to measure this construct well.