The flugelhorn is a member of the horn family, specifically the brass family, which in turn is a member of the wind instrument family (Aerophones). Instrument scholar Anthony Baines describes it as a valve bugle which is related to both the key bugle (a precursor of the bass saxophone, which was replaced by the tuba in orchestras) and the signal horn (a bugle used as a signal in battle).

Flugelhorns have a short, wide mouthpiece; three or four valves; and a flared bell. They range in size from bass instruments with wider bores (the bore is the inside diameter of the tubing) to small soprano horns in f or e flat. To the casual observer, a flugelhorn looks very much like a trumpet or cornet. Inasmuch as it belongs to the instrumental family called the brass, is traditionally made of a brass or a brasslike material, although there are valveless models made of clay. Its range is two and a half octaves, and it is approximately nineteen inches long.

The flugelhorn is basically a bugle, pitched in B flat with valves. It has a larger bell; a wider bore; and a larger, deeper mouthpiece than its predecessor. Thus, it produces a much more mellow sound. Although the flugelhorn is primarily used for military bands, it has been utilized by some contemporary composers for orchestral music.