This study investigates the link between process evaluation components and the outcomes of a school-based nutrition curriculum intervention, "Choice, Control and Change". Ten New York City public middle schools were recruited and randomly assigned into intervention or control condition. The curriculum was to improve sixth to seventh grade students' energy balance related behaviors, based on social cognitive and self-determination theories, and implemented during the 2006-2007 school year (n = 1136). Behaviors and psychosocial variables were measured by self-reported questionnaires. Process components were evaluated with classroom observations, teacher interviews, and a student questionnaire. Using "Teacher Implementation" (dose delivered) and "Student Reception" (dose received) process data; intervention group was further categorized into medium- and high-implementation groups. Analysis of covariance revealed that, compared with control group, only high-implementation group showed significant improvement in students' behavior and psychosocial outcomes. Hierarchical linear models showed that "Teacher Implementation" and "Student Reception" significantly predicted students' sweetened beverage outcomes (P < 0.05). "Student Satisfaction" was also greater when these implementation components were higher, and significantly associated with behavior and psychosocial outcomes (P < 0.05). Implementation process influenced the effectiveness of the "Choice, Control and Change" intervention study. It is important to take into account the process components when interpreting the results of such research.