This multiple case study explores how researchers are motivated to perform their third mission activities in terms of collaborative projects with public and private actors. The study also investigates the involvement of universities' third mission support personnel and technology transfer executives in the collaboration. The study contributes new insights into individual motivations for academic engagement and commercialisation. This is done by empirically demonstrating that commercialisation projects are based on ideas originated from novel and basic research, while academic engagement is based more on the general knowledge and capabilities of researchers and their research groups. The findings also revealed that motivations for taking on third mission activities were mainly about disseminating the results of research to wider society, rather than being driven by monetary rewards. This is demonstrated not only for the researchers, but also for the external partners, the support personnel, and technology transfer executives. The findings further imply that researchers are more satisfied with the support structure set up at their university for academic engagement projects than with the support structures for commercialisation of research, such as technology transfer offices. The findings can have implications for both policymakers and practitioners within knowledge and technology transfer.