While it has been widely documented that mobile users tend to differ from PC users in their observed behavior, such differences cannot necessarily be attributed to adoption of the mobile app because of endogeneity issues in drawing inferences from observing users who decide to adopt the mobile app. In this paper, we causally explore the changes in user behavior as well as matching outcomes due to adopting a mobile app in the online dating context. We demonstrate that once users have adopted the mobile app, they become more ubiquitous in their use and also become more socially engaged. We also find that female adopters are able to achieve more matches and become more efficient in achieving matches per each message sent. As mobile app adoption becomes widespread, understanding the causal impact on social engagement and outcomes has implications for both end users as well as businesses investing in app development.