Evidence suggests early events might modify adult breast cancer risk and many adolescents learn of familial and genetic risks for breast cancer. Little is known about how adolescent girls understand and respond to breast cancer risk. Semi-structured interviews with 11-19 year-old girls at high-risk and population-risk for breast cancer evaluated knowledge and perceptions of breast cancer risk and risk modification. Framework analysis and descriptive statistics were utilized to analyze open-ended responses. Risk group and age differences were evaluated by Fisher's exact and McNemar's tests. Fifty-four girls (86 % of invited), 35 high-risk (65 %), and 19 population-risk (35 %) completed interviews. The most frequently reported risk for breast cancer was family history/hereditary predisposition (66 %). Only 17 % of girls were aware of BRCA1/2 genes. The majority (76 %) of high-risk girls perceive themselves to be at increased risk for breast cancer, compared to 22 % of population-risk girls (p = 0.001). Half of girls reported that women can get breast cancer before 20-years-old. The majority believe there are things women (70 %) and girls (67 %) can do to prevent breast cancer. Mother was the most frequently reported source of information for breast cancer among both high-risk (97 %) and population-risk (89 %) girls. In this study, many high-risk girls perceive themselves to be at increased risk for breast cancer, and many girls believe that breast cancer can occur in teens. Yet, most girls believe there are things women and girls can do to prevent breast cancer. Research evaluating the impact of awareness and perceptions of breast cancer risk on psychosocial, health, and risk behaviors is needed to develop strategies to optimize responses to cancer risk.