Although the settlement of Warminster dates from Saxon times, the downs around the today's town were occupied by Iron Age people who left their earthworks, including hill forts and barrow mounds, behind them. Battlesbury Camp is one of the major Iron Age hill forts in Britain.

Warminster's later history was peaceful and prosperous. In the Middle Ages the town became famous not only for its wool and cloth trade but also for its great prosperity as a corn market (it was second only to Bristol in the West of England). Many of the buildings which survive in the Market Place owe their origin to the great corn market days when they were used as stores and warehouses, or as inns and hostelries for the buyers and sellers who came from many miles around.

During the Civil War (1642-1645) the town is thought to have changed hands at least four times between the Royalist and Parliamentary supporters. When James II came to the throne in 1685 the local gentry and the Wiltshire Militia supported him against the Duke of Monmouth who was defeated.

When the writer William Cobbett visited the area in 1826 he found it a fertile and productive region of, for the most part, arable farming with also the rearing of thousands of sheep. He said the stock production yielded "beautiful meat - the best I have seen anywhere." And, he described Warminster as "solid and good."

During the First World War thousands of soldiers from Australia, New Zealand and Canada were camped in the villages around Warminster, prior to the invasion of France. Sutton Veny and Codford have ANZAC cemeteries (here lay the victims of a flu epidemic) and an annual ANZAC Day service is held on the Sunday nearest to 25th April. Buildings in the town were used as billets for American troops during the Second World War and among the celebrities who came to entertain them were film star James Cagney and boxer Joe Louis.