This study aimed to assess the impact of educational intervention, based on health belief model (HBM) and collaborative learning techniques on diet quality in adolescents. In this field trial study, 311 students aged 13-15 years old were included, of which 163 and 148 allocated in the experimental and comparison groups, respectively. They were selected through a stratified random sampling from 16 urban, secondary schools in 4 educational districts of Shiraz, the largest city in southern Iran. The revised children diet quality index was used to assess their diet quality. Using HBM as a framework for targeting determinants of dietary behavior, the intervention was performed in a collaborative learning context during the educational year (2015-16). Constructs of HBM and diet quality were measured before and after the intervention. All HBM's constructs and knowledge had significantly improved in the experimental group and mean differences were increased after the intervention. Diet quality improved in the experimental group (P < 0.001), which was significantly different from the comparison group (P = 0.001). The findings support the integration of appropriate models/theories into the context of collaborative learning methods to target large number of behavioral determinants, and ultimately increase the effectiveness of the educational interventions amongst adolescents.