Designers are increasingly playing a strategic role in innovation projects. They can do this, amongst others, by more effectively collaborating with the managers of these projects. This thesis investigates the antecedents and consequences of effective collaboration between designers and managers in innovation projects. It builds on findings from the design and innovation management literatures, which have suggested that the main antecedents of effective collaboration between designers and managers are their different ways of working and cognitive styles, as well as the management of these differences in terms of the decision freedom granted to designers. Moreover, the design and innovation management literatures have proposed that the main consequences of effective collaboration between designers and managers are higher levels of financial, market and process performance. This thesis extends the findings from the design and innovation management literatures by conducting three studies on these antecedents and consequences which fill the gaps in prior research. The findings from these three studies show that designers and managers should adopt each other’s way of working and cognitive styles as well as cherish their differences to collaborate effectively, and they show that there is a need for granting designers the freedom to make decisions on their own as well for making decisions together with managers. In addition, the results from this thesis contribute to the research on the consequences of effective collaboration between designers and managers by proposing that the two need each other’s cognitive styles and they need to make decisions together to achieve high levels of financial and market performance, while designers can make decisions on their own to achieve process performance (both in terms of meeting budget and planning goals as well as achieving high product innovativeness).