This article assesses the role of investments in intangible capital and their potential complementarities as a way to improve firm productivity. We focus on the three intangible resources that, according to the literature, have the greatest strategic importance: research and development (R&D), advertising, and human capital. To test our hypotheses, we use a large sample of Spanish manufacturing firms and consider estimates of total factor productivity through a generalized method of moments approach. Our results show evidence of complementarities between R&D and advertising investments and between advertising and human capital. However, they are not conclusive in the case of R&D and human capital.