Epidemiological studies have shown a positive correlation between the incidence of coronary heart disease and elevated levels of total cholesterol, low-density lipoprotein (LDL), and triglycerides, as well as lower levels of high-density lipoprotein (HDL) in blood. The aim of this study was to compare the effects of the addition of evening primrose seeds and safflower seeds on selected morphological and biochemical blood parameters of experimental rats on a high-fat diet. The experiment was performed on 30 rats (male and female) of the Bufflo strain. The animals were divided into 3 groups, which were fed a high-fat diet and herbal supplements. It was shown that both evening primrose seed and safflower seed, added to the diet, resulted in reduced levels of triglycerides in blood. They had no effect on cholesterol. These vegetable supplements also changed some of the morphological parameters of blood, including the number of leukocytes.