Background and Objective: Energy and nutrient needs of pregnant women increase significantly during pregnancy. Continuing education on pregnancy diet and providing proper nutrition is necessary to promote the health of both mother and fetus. The aim of this study was to evaluate the effectiveness of antenatal preparation for childbirth courses on the pregnant women nutritional behavior. Materials and Methods: This was a clinical experimental study performed on 280 pregnant women expecting their first childs. They were randomly divided into the test and control groups. Women in the test group were trained both theoretically and practically for eighth 90-minute sessions. By contrast, those in the control group received routine care only. Data collection was conducted in two phases: pre- and post-test. Data were analyzed by SPSS software using chi-square and t-Test. Results: There were no significant differences between the two groups with regards to age, body mass index (BMI), education level, age, and employment status. There was no significant difference in nutritional behavior between the two groups pre-intervention (P=0.238). However, following the intervention, the amount of nutritional behavior in the test group (38.12 +5.54) was significantly higher than the controls (29.12 +11.12), (P<0.0001). Conclusion: Our findings show that arragnement of pregnancy courses had a positive effect on mothers’ nutritional behavior. Thus, implementing this program as a continuous intervention for pregnant mothers is recommended.