Yellow starthistle reduces land value for recreation and for livestock foraging because of its large spines and dense growth pattern.

It also uses large amounts of water, reducing soil moisture levels and impacting native plant species.

Yellow starthistle directly competes with native plants, reducing their distribution and seed output.

When yellow starthistle is eaten by horses, it causes a neurological disorder similar to Parkinson's disease.   Chronic exposure results in symptoms known as "chewing disease".  There is no treatment and it is fatal to horses.  Horses are the only animal known to be affected in this way.

Honeybees (another European import) utilize the plant for pollen and nectar, which they use to produce high quality honey.

Prior to blooming, yellow starthistle provides a high protein forage for cows and sheep.  After flowering, the protein content drops rapidly.