Widespread in the Mediterranean region, fennel (Foeniculum vulgare) is a biennial, aromatic, and medicinal plant distinguished by its feathery leaves, umbels of yellow flowers, hollow stem, and scented seeds. Phytochemical profiles of the waste components of fennel (F. vulgare) were described for the leaves, bulb, and stems. Several compounds from flavonoid glycosides, flavonoid aglycones, hydroxycinnamic acid derivatives, iridoid derivatives, phenolic acids, and lignans were detected. Additionally, there was relief from the presence of several oxylipins. Numerous metabolites found in F. vulgare have biological potential, such as immunomodulatory, antioxidant, and anti-inflammatory traits. This chapter highlighted phytochemicals from fennel (Foeniculum vulgare) by-products.