AbstractSelenium is a micronutrient element that is beneficial for the growth and development of plants. It has antioxidant, anticancer, and antiviral properties that are essential for human and animal health. Low‐consumption mineral elements such as selenium can be included in the diet from various sources. To investigate the growth and phytochemical attributes of a broccoli cultivar “Heracklion”, an experiment with five levels of selenium concentration (0, 5, 10, 15, 20 mg/L sodium selenate) was carried out in a randomized complete block design with 3 replications in the field condition. With increasing the concentration of sodium selenate in the foliar application, the accumulation of sodium selenate in broccoli increased and the highest amount (1.47 mg/kg dry weight) was measured at 20 mg/L of sodium selenate. The highest amount of photosynthetic pigments in leaves was recorded at 15 mg/L of sodium selenate. In the case of glucosinolates, with increasing selenium concentration up to 20 mg/L concentration, glucoraphanin, 4‐methoxy glucobrassicin, and aliphatic glucosinolates increased in leaves. It could be demonstrated that foliar application of selenium at 10 mg/L led to an improvement of secondary metabolites, especially glucoraphanin, both in leaves and florets, and could also have a positive effect on human nutrition.