As platform owners continue to expand their ecosystems, many of them have started to provide consumers with their own complementary applications. These moves position the platform owners as direct competitors to their complementors. This paper surveys empirical studies that examine the direct entry of platform owners into complementors’ product spaces. It finds that both the motivation and impact of such entries on complementors are multifaceted. The motivation behind platform owners’ direct entry goes beyond value capture, and the impact of platform entry on complementors varies across empirical settings. It identifies several future research directions that can help advance our understanding of the relationships between platform owners and complementors.