The aim of this study was to examine sleep habits (i.e., bedtimes and rising times) and their association with nighttime text messaging in 15- to 17-year-old adolescents. This cross-sectional study analyzed data from a web-based survey of adolescent students attending secondary schools in southern Sweden (N = 278, 50% female). Less than 8 hr of time in bed during school nights was significantly associated with more sleep difficulties, wake time variability on school days and weekends, daytime tiredness, and less enjoyment at school (all ps < 0.05). Sending and/or receiving text messages (Short Message Service [SMS]) at night was significantly associated with later bedtimes, shorter time in bed, daytime tiredness during school, and irregular sleep habits (p < 0.05). These findings highlight the importance of regular, consistent sleep habits and the problems associated with sleeping with a cell phone in the bedroom.