Issue addressed: Childhood obesity is a serious public health challenge. Consumption of sugar-sweetened beverages (SSBs) is one contributing factor, with adolescents being the highest consumers. Methods: This study used a randomised controlled trial and two-by-two factorial design to determine the effectiveness of a school-based behavioural intervention (including education/promotional messages) and/or environmental intervention (chilled water station), on encouraging adolescents to choose water instead of SSBs. Sixty-one secondary schools (n = 8992 eligible students year 7 student) were recruited and randomly allocated to one of four study groups, the behavioural intervention, the environmental intervention, both interventions or neither. Results: The primary outcome was increased water consumption; secondary outcomes included changes in students' knowledge and attitudes about water and SSBs and changes in SSB consumption. For students who received at least one intervention there was an increased odds (though not statistically significant) of higher water consumption compared to those that received no intervention. There was a decrease in SSB consumption for students who received both interventions combined (OR: 0.67; 95% confidence interval: 0.55-0.082; P <.01). Conclusions: The combined intervention had a greater effect on decreasing SSBs consumption. This is noteworthy given SSBs are a key contributor to overweight and obesity. So what?: To our knowledge this is the first Australian study examining combined school-based interventions to specifically promote the consumption of water and decrease the consumption of SSBs in adolescents. The study findings add to the evidence regarding the benefits of delivering multicomponent school-based interventions which add value to existing interventions that address the complex public health issue of overweight and obesity.