The American Academy of Pediatrics recommends infants' exposure to electronic screen-based media be minimized; however, more research is needed to understand effects of viewing screen-based media. Here, we examine relations between media use and sleep. Data were collected from mothers when their infants (N = 429) were four months of age. Mothers answered questions about the time their infants spent watching electronic screen-based media. Exposure to electronic screen-based media was negatively associated with nighttime sleep (but not daytime sleep), such that an hour of screen time was associated with nearly 13 min less sleep on a typical night.