Recent advancements in communication technology have enabled billions of people to connect over great distances using mobile phones, yet little is known about how the frequent presence of these devices in social settings influences face-to-face interactions. In two experiments, we evaluated the extent to which the mere presence of mobile communication devices shape relationship quality in dyadic settings. In both, we found evidence they can have negative effects on closeness, connection, and conversation quality. These results demonstrate that the presence of mobile phones can interfere with human relationships, an effect that is most clear when individuals are discussing personally meaningful topics.