Introduction: Weight problems not only affect adults, but youth as well. Excessive sugar-sweetened beverage (SSB) consumption is suggested to be a contributor to youth overweight and obesity and other cardiometabolic risk factors. Parents, although probably not readily admitted by adolescents, are known to influence youth's dietary beliefs and practices. Using theoretical models, like the Theory of Planned Behavior (TPB) that accounts for intention, attitudes, norms, and perceptions of control, to develop interventions can be more effective in changing health-risk behaviors versus those not grounded in theory. Methods: A systematic literature review and meta-analysis on how the TPB has been applied to youth's diet-related behaviors was conducted. Subsequently, a mixed methods investigation of adolescents' (n=100) and parents' (n=66) SSB consumption and exploratory analysis of parents' responses to adolescents' beverage choices was carried out. Results: From 34 articles, attitude was identified as having the strongest relationship with behavioral intention (mean r=0.52), and intention as the most common predictor of youth's diet-related behavior (mean r=0.38, both p<0.001). However, in the mixed methods analysis adolescents' subjective norm was the strongest predictor of intention to limit sugary beverage consumption to less than one cup per day (b=0.57, p=0.001). Intention was the strongest predictor of SSB intake in parents and adolescents (b=-47, p=0.01; b=-37, p≤0.05). The TPB explained more variance in parents' SSB consumption than adolescents' (R²=0.22 versus R²=0.38, both p≤0.001, respectively). At lower levels of intention to limit SSB consumption and higher levels of parental encouragement to consume SSBs, adolescents' predicted SSB intake was highest (p=0.059) suggesting that some adolescents may be influenced by their parent's reactions to their sugary beverage choices while others may not. Conclusions: Intention appears to be a strong construct influencing adolescents' diet-related behaviors, specifically SSB consumption, and this intention may be influenced by parents and other social factors. Future work can tap into adolescents' peer network and role models or authority figures to identify how these groups and individuals influence and moderate the intention to limit sugary beverage consumption.