This study examines the relationship between personal network characteristics and innovation performance. Specifically, it investigates the effects of two properties of personal networks on actors’ propensities to engage in innovation activities: network sparseness and network diversity. The study contributes also to decoupling social network structure and individual agency (i.e. tertius iungens orientation) as critical factors influencing engagement in innovation. The study highlights the importance of a particular strategic behavioral orientation of individuals to coordinate and mobilize network resources to foster the implementation of innovative ideas. Our findings show an inverted U-shaped relationship between network sparseness, network diversity and innovation, and a positive moderating role of a tertius iungens orientation on the curvilinear relationship between both network properties and innovation. Our hypotheses are tested on a large sample of Spanish biomedical scientists working in diverse institutional settings.