INTRODUCTION: Mothers and children are the most vulnerable members of every society. As a result many deaths occur in these two groups, so caring for these two groups is very important. Today, it is believed that the health of an infant is related to the health of their mother. Maintaining a healthy weight before pregnancy, and optimal weight gain during pregnancy by appropriate and sufficient nutrition, are two effective measures for the prevention of low birth weight.To provide successful health interventions, it is essential to design and implement effective health education programs. Successful education also depends on the proper use of theories and models in health education. The Health Belief Model is a model that illustrates the relationship between beliefs and health, and it is based on the hypothesis that preventive health behavior consists of personal beliefs .The aim of this study was to assess the effects of training on the Health Belief Model on dietary behaviors of a sample of pregnant Iranian women. MATERIALS AND METHODS: This study was a randomized controlled clinical trial, involving 130 pregnant women who attended two health care centers of Shahid Beheshti University of Medical Sciences. Data was collected by a structured questionnaire in three parts and seven sub-scales (including demographic characteristics, knowledge and dietary behaviors) based on the Health Belief Model. Principles of education were based on the Health Belief Model and performed twice during two-hour sessions in the intervention group. Women in the control group received routine care and did not receive training on the above model. In order to evaluate the intervention, the previously mentioned questionnaire was administered one month after completion of the intervention, and filled by participants in both groups. Data were analyzed by SPSS software and reported with diagrams and tables. RESULTS: The mean score for each variable before the intervention, except for the performance guide variable, was not significantly different between the two groups (p<0.05). A month after the intervention, the mean scores of the knowledge, perceived severity, perceived benefits in each group, were significantly different. These results demonstrated that there were significant differences between the two groups in terms of mean scores of knowledge, perceived severity, perceived barriers, performance guide and individual performance, and the means of these variables in the intervention group were also higher than the control group. On the other hand, after the intervention, there was no statistically significant difference found in the mean scores of perceived benefits and perceived susceptibility between the two groups (two independent samples t-test, P <0/001). CONCLUSION: Educational interventions based on health promotion patterns can be effective in enhancing awareness, better understanding of risks, reducing barriers to healthy behavior and ultimately, improving women's health and nutritional performance during pregnancy.