This paper evaluates whether university-industry relationships (UIR) and academic research activities have complementary effects on the scientific production of university lecturers. The analysis is based on a case study of two Spanish universities. We find that the effects of R&D contracts with industry, and academic research activity on scientific production are synergistic, but only when the R&D contracts account for a low percentage of a lecturer's total funding. This suggests that the positive effect of UIR on a lecturer's scientific production comes fundamentally from the capacity to provide complementary resources (cognitive, technical, and/or financial) for research activities. If lecturers are not involved in research and dedicate most their time to the development of activities related to UIR, their scientific production will be negatively affected.