Using a complexity lens has not gained widespread attention for explaining why certain planning processes succeed and others fail. This chapter responds by proposing Qualitative Comparative Analysis (QCA) as a method for analyzing the performance of spatial planning processes, taking into account the perceived complexity of the contextual environments encountered. This proposal is rooted in a contingency perspective. Contingency perspectives assume that, for spatial planning approaches and organizational formats to perform well, they should be adapted to the environment in which they intend to operate; i.e., a degree of ‘fit’ is required. The perceived complexity of the contextual environments is among the key arguments contingency studies ...