At rest or at work, unridden or ridden, signs of agitation might include vocalization (whinnying) pacing, pawing, head tossing, among others. A "pinched" facial expression, teeth grinding and elevated heart rate are examples of more subtle signs of a stressed horse.

Excessive agitation or nervousness may be considered normal for some horses, but also may be the cause or result of potentially serious health-related issues. Abdominal pain (colic) can look like agitation, however excessive stress also makes colic and injury more likely.

Certain conditions are thought to be more common in horses with nervous dispositions. A notable example of this is Recurrent Equine Rhabdomyolysis (one form of "tying up"). Changes in management can also cause stress. A herd member will become very agitated if removed from the herd.