To assess knowledge, beliefs, and practices of osteoporosis risk factors (physical activity, smoking, and nutrition) among adolescent girls. Questionnaires consisting of items assessing knowledge, beliefs, and practices regarding physical activity, calcium intake, and cigarette smoking were administered to 227 girls aged 12–16 years. The adolescent girls were attending public and separate schools in a small-sized Canadian city. Descriptive statistics, t-tests, and Chi-square tests were used to analyze the data. Female adolescents believed that physical inactivity, smoking, and inadequate calcium were health-risking behaviors and osteoporosis risk factors, however, specific in-depth knowledge regarding these risk factors was lacking. Findings further showed that health-risking behaviors were evident, as 25% were current smokers, 58% consumed less than the adequate intake for calcium, and 52% had scores that reflected low to moderate physical activity levels. These results highlight the need for educational interventions to promote specific osteo-protective practices among adolescent girls.