We study the effect of horizontal minority stake acquisitions on firms’ innovation incentives and patenting behavior. Using patent data from 34 countries between 2001 and 2019, we employ a staggered, matching-based difference-in-differences approach, complemented by an event study. We find that such acquisitions lead to a decline in both the number of patents granted and the number of citations received, indicating a reduction in innovation activity. These results suggest that horizontal minority acquisitions can serve as a mechanism to soften rivalry, not only in product markets, but also in innovation.