Patent Pledges are initiatives of patent owners in which they announce the free or reasonable availability of active patents. Many firms struggle to understand the rationales behind these strategies, making it difficult to decide whether or not to trust them. After all, respective patent owners could also let the patents lapse to make them available. So, what do patent owners hope to achieve through these initiatives? Existing literature suggests motives for patent pledges, but lacks academic rigor and empirical evidence. To further our understanding of patent pledges, we conducted 30 expert interviews, including people directly involved in the decision to initiate and to execute patent pledges. As a complementary data source, we qualitatively analysed 50 public patent pledge statements with respect to their underlying motives. We found 13 distinct motives belonging to three general categories, the primary motive being ‘Driving Technology Diffusion’. We contribute to existing knowledge by providing novel insights into the phenomenon of patent pledges and empirical evidence to what the literature has suggested. We argue that all motives of free patent pledges link to the overarching goal of fostering technology diffusion.