The present study was designed to assess the toxic effects of a nitrogen fertilizer widely used in Algeria, calcium nitrate, on hematological and biochemical parameters and on certain histological changes in the liver and kidneys of white male rats of the Wistar strain. The results indicate that treatment of rats with calcium nitrate under the experimental conditions of this study resulted in a significant increase in body mass, as well as an increase in absolute and relative liver mass in the high-dose groups. Disturbances in haematological parameters and changes in biochemical parameters were observed in high-dose rats. In the histological study, microscopic observation showed altered liver and kidney tissues in the various treated groups compared with the untreated group. In conclusion, the overall results showed that exposure to calcium nitrate caused disturbances in the organism, manifested by altered liver and kidney function parameters.