This study aimed to investigate prospective predictors and health-related outcomes of positive body image in adolescent girls. In so doing, the modified acceptance model of intuitive eating was also examined longitudinally. A sample of 298 girls aged 12 to 16 years completed a questionnaire containing measures of body appreciation, potential predictors, and a range of health outcomes, at 2 time points separated by 1 year. Longitudinal change regression models showed that perceived body acceptance by others (positively), self-objectification and social comparison (negatively), and body appreciation (positively) prospectively predicted intuitive eating 1 year later, consistent with the acceptance model of intuitive eating. Perceived body acceptance by others was the only proposed predictor to prospectively predict an increase in body appreciation over time. Time 1 body appreciation prospectively predicted a decrease in dieting, alcohol, and cigarette use, and an increase in physical activity 1 year later. In particular, girls with low body appreciation were more likely than girls with high body appreciation to take up alcohol and cigarette use between time points. The results highlight body appreciation as an important target for interventions designed to prevent or delay the uptake of alcohol and cigarette consumption among girls. More broadly, they suggest that a positive body image can confer considerable benefit for adolescent girls.