Kohlrabi (Brassica oleracea var. gongylodes) is a vegetable of the cruciferous family (Brassicaceae). Based on the color of kohlrabi, it is classified as purple or pale green kohlrabi. Kohlrabi by-products include mainly peels, sprouts, leaves, and seeds, with several phytochemicals being reported from these by-products, such as anthocyanin, flavonoids, glucosinolates, indoles, phenolic acids, and phytosterols. Phytochemicals from kohlrabi by-products possess several biological activities, including anti-hyperalgesic, anti-inflammatory, anti-hyperglycemic, antibacterial, and antioxidant activities. Other health benefits from kohlrabi by-products include blood pressure lowering, cholesterol reduction, cancer-fighting, chemopreventive properties, and weight loss adjuvant. Furthermore, kohlrabi by-products have demonstrated promising applications in silver and gold nanoparticle synthesis, fermented vegetables, functional food formulation and packaging with potent antioxidant, antibacterial, and UV-blocking properties and extended shelf life and preservation properties. This chapter presents the latest research and development on the kohlrabi by-products regarding bioactive phytochemicals, biological activities, and their potential industrial applications.