Self-reported short sleep duration is linked to higher blood pressure and incident hypertension in adults. Few studies have examined sleep and blood pressure in younger samples. We evaluated the associations between actigraphy-assessed time spent asleep and ambulatory blood pressure in adolescents. Participants were 246 black and white adolescents (mean age: 15.7 years) who were free from cardiovascular or kidney disease and were not taking sleep, cardiovascular, or psychiatric medications. Sleep duration and efficiency were assessed with in-home wrist actigraphy and sleep diaries across 1 week; ambulatory blood pressure monitoring was used to obtain 24-hour, sleep, and wake blood pressure, as well as sleep:wake blood pressure ratios across 2 full days and nights. Results showed that shorter actigraphy-assessed sleep across 1 week was related to higher 48-hour blood pressure and higher nighttime blood pressure. Shorter sleep was also related to a higher systolic blood pressure sleep:wake ratio. These results were independent of age, race, sex, and body mass index. Follow-up analyses by race revealed that associations between sleep duration and blood pressure were largely present in white, but not black, adolescents. These data are consistent with the hypothesis that the cardiovascular consequences of short sleep may begin as early as adolescence.