The bulb, foliage, and seeds of the fennel plant are used in many of the culinary traditions of the world. The small flowers of wild fennel (known as fennel "pollen") are the most potent form of fennel, but also the most expensive. Dried fennel seed is an aromatic, anise-flavored spice, brown or green in color when fresh, slowly turning a dull grey as the seed ages. For cooking, green seeds are optimal. The leaves are delicately flavored and similar in shape to those of dill. The bulb is a crisp vegetable that can be sauted, stewed, braised, grilled, or eaten raw. Young tender leaves are used for garnishes, as a salad, to add flavor to salads, to flavor sauces to be served with puddings, and also in soups and fish sauce.

Fennel seeds are sometimes confused with those of anise, which are similar in taste and appearance, though smaller. The seeds are used in cookery and sweet desserts.