Objective: The food additives, like sodium nitrite and nitrate, are used in many food products to prevent the growth of yeasts and molds. The histopathological effects of sodium nitrite in various tissues such as liver and kidney have been reported, but there has been no report about the histopathological effects on the embryonic organ development. Materials and Methods: 100 Gallus gallus fertilized eggs were incubated, then second branchial arches were separated on day 4 at stage 24, and divided into 4 groups which included a control and 3 experimental groups that were treated with 2000, 1000 and 500 μg/ml dosages of sodium nitrite. They were cultured for 7 days. For microscopic studies, the specimens were fixed, and the tissue passage was done. The tissue sections were stained with Hematoxylin-eosin, Toluidine blue, and the histopathological changes (including the number of cells and nucleus diameter) were evaluated. All data were analyzed by using SPSS/16 software (p<0.05). Results: The results showed that the mean number of cells from day 2 to day 7 in the experimental group treated with 2000μg/ml sodium nitrite were significantly decreased in comparison with the control (p<0.05) and the mean diameter nucleus from day 2 until day 7 in the experimental group (2000μg/ml) was also significantly decreased in comparison with the control (p<0.05). Histopathological studies showed the formation of cartilage matrix in the control and experimental groups (1000 and 500 μg/ml sodium nitrite). Conclusion: Considering the results of this study and the other studies, sodium nitrite can cause organ and tissue damages.