This paper aims to describe the prevalence of parent-adolescent conversations about eating, physical activity and weight across sociodemographic characteristics and to examine associations with adolescent body mass index (BMI), dietary intake, physical activity and sedentary behaviors. Data from two linked epidemiological studies were used for cross-sectional analysis. Parents (n = 3,424; 62 % females) and adolescents (n = 2,182; 53.2 % girls) were socioeconomically and racially/ethnically diverse. Fathers reported more parent-adolescent conversations about healthful eating and physical activity with their sons and mothers reported more weight-focused conversations with their daughters. Parents of Hispanic/Latino and Asian/Hmong youth and parents from lower socioeconomic status categories engaged in more conversations about weight and size. Adolescents whose mothers or fathers had weight-focused conversations with them had higher BMI percentiles. Adolescents who had two parents engaging in weight-related conversations had higher BMI percentiles. Healthcare providers may want to talk about the types of weight-related conversations parents are having with their adolescents and emphasize avoiding conversations about weight specifically.