Selenium (Se) is a naturally-occurring non-metallic element that serves as an essential micronutrient for humans and animals. Insufficient intake of Se by mammals can contribute to the onset of “Keshan disease” and “white muscle disease”, whereas excessive amounts can lead to toxicoses (Fordyce 2013). Cordyceps militaris is a highly nutritious ascomycetous fungus which is one of the most popular edible and medicinal mushrooms worldwide. The benefits of consuming C. militaris are due to its pharmacological functions affecting the circulatory system, as well as its antioxidant, anti-tumor, anti-metastatic, immunomodulatory, anti-inflammatory, and anti-bacterial activities (Das 2010). This study describes the development of Se-biofortified C. militaris fruiting bodies that combine the functions of the essential trace element and the medicinal properties of the mushroom in a potential dietary supplement. The presented results provide novel insights relevant to the cultivation of Se-biofortified C. militaris fruiting bodies.