The yellow flowers of the plant produce hairy seed pods, with each pod containing roughly a half dozen seeds. These seeds are harvested just prior to the pods becoming ripe and bursting.

White mustard seeds are hard round seeds, usually around 1.0 to 1.5 mm (0.039 to 0.059 in) in diameter, with a color ranging from beige or yellow to light brown. They can be used whole for pickling or toasted for use in dishes. When ground and mixed with other ingredients, a paste or more standard condiment can be produced.

The seeds contain sinalbin, which is a thioglycoside responsible for their pungent taste. White mustard has fewer volatile oils and the flavor is considered to be milder than that produced by black mustard seeds.

In Greece, the plant’s leaves can be eaten during the winter, before it blooms. Greeks call it vrouves (βρούβα) or lapsana (λαψάνα). The blooming season of this plant (February–March) is celebrated with the Mustard Festival, a series of festivities in the wine country of California (Napa and Sonoma Counties).