Background: Wellness is a multidimensional construct related to an individual's physical, emotional, intellectual and social well-being. We present estimates of wellness among US adolescents aged 12-17 years and explore how demographic characteristics are associated with wellness. Methods: All respondents aged 12 to 17 years (n=34601) from the 2011-2012 National Survey of Children's Health were included in the sample. Survey items were coded to operationalize an overall wellness score, comprised of four subdimensions (physical, intellectual, emotional and social). Results: The mean adjusted overall wellness score was 30.2 (out of 40). Mean raw subdimensions scores were: social = 3.14 (out of 4), emotional = 4.79 (out of 6), intellectual = 4.80 (out of 8) and physical = 6.57 (out of 8). Older adolescents, those with special health needs, those in lower income families and those whose mother or father report fair-poor mental health status had lower wellness scores. Conclusions: US adolescents have wellness scores towards the upper or higher end of our scale. Several adolescent and family characteristics were associated with either lower overall wellness and/or lower wellness on multiple subdimensions. Assessing wellness during critical developmental periods of adolescence is a first step towards promoting behaviours that support increased wellness into adulthood.