At some point before the First Century BC a contour hill fort was constructed on Milber Down above Milber, now home to a housing estate on the south east of the town. It was later briefly occupied by the Romans.

Similarly the remain of a Norman motte-and-bailey castle, known as Castle Dyke, are on Highweek Hill, today a suburb to the north west. A village grew up around the castle, first called Teignwick, and later Highweek, before being renamed Newton Bushel during the thirteenth century after the then lord of the manor, Robert Bushel. In 1309, as the manor developed, Bushel obtained the right to hold fairs on All Saints Day and at Ascension tide, as well as a weekly market very Tuesday beside old St Mary’s Chapel.

At the same time another settlement developed on the low ground on the opposite bank of the River Lemon, known as the New Town of the Abbots of Torre Abbey, who themselves were to be found in nearby Torquay. Here, at some point between 1247 and 1251, the right to hold a weekly market on Wednesdays was also granted. This market thrived, providing the Abbots with a good source of income, and the settlement of Newton Abbot quickly grew.

Over the next 200 years Newton Bushel ran more annual fairs, a number of mills were set up and the leather and wool trades started. Devon was an important sheep rearing county and Newton Abbot also had woollen mills, fullers, dyers, spinners, weavers and tailors. The town was also home to a number of tanners, boot and shoe makers, glovers and saddlers.

Between 1600 and 1850 there was a steady trade between Newton Abbot and the cod fisheries off Newfoundland. Each year, men from the town would gather at the Dartmouth Inn or Newfoundland Inn in East Street in the hope of being hired for a season’s work. In the autumn the dried cod was stored in depots and sometimes used as payment. At the same time, fish hooks, knives, waterproof boots and rope were all made in the town. The Rope Walk in East Street still exists, along with the names of Newfoundland Way and St John’s Street.

In 1663 the markets of the two towns were combined as a single Wednesday market in Newton Abbot and, by 1751 there was also a smaller Saturday market and three annual fairs. A cattle fair was held each June, a cheese and onion fair in September and a cloth fair in November, the town’s busiest. In 1724 Daniel Defoe wrote that Newton Abbot had a thriving serge industry, the worsted variety of which was used in making military uniforms, suits, great coats and trench coats, sending goods to Holland via Exeter.

In subsequent years the markets continued to expand, so in 1826 a new market was built. However by the end of the 1860s this had become dilapidated, so in 1871 the River Lemon was covered over and it was replaced with a substantial new complex whose buildings included a pannier market, a corn exchange and a public hall. This was enlarged again in 1938 when a new cattle market and corn exchange were built. During the nineteenth century Vicary's mills became an important employer, providing work for over 400 men by the 1920s. The works finally closed in 1972.

In 1688 William of Orange made his first proclamation after landing at Brixham from the pedestal of the town’s market cross. William III, Prince of Orange, landed in Brixham on 5 November, 1688 and his first declaration was read that day by the Rev John Reynell, standing on a pedestal adjacent to the ancient tower of St Leonard in the town centre. However William himself only arrived in Newton Abbot the next day, stopping overnight in the town at Forde House as he made his way to London to assume the English throne.

On 30 April 1846 the South Devon Railway opened the town’s railway station and shortly after constructed two small road sheds. By 1851 the facilities had expanded to encompass an engine shed, used for lighting and cleaning engines; a large repairing shop; a smiths' shop fitted with six hearths and bellows; a store room; a boilerhouse boasting a high chimney; a 34ft wooden turntable; and two water cranes with pipes to the tanks. In 1876 the Great Western Railway purchased the South Devon Railway, developing the repair and maintenance sheds into a substantial works employing over 600 men, a number that grew to more than 1,000 by 1930. 1892 saw the construction of a new engine shed and workshops, later retained to service British Rail diesel locomotives, but subsequently closed in 1981.

In addition to the railway, according to John Bartholomew's Gazetteer of the British Isles published in 1887, the chief industries of the town were brewing, iron-founding, and tanning. There was also a considerable trade in corn, timber and potter's clay, for the loading of which large and convenient wharves had been been erected.

Such was the growth of the town during the nineteenth century, the population increased by more than 670%, from 1,623 in 1801 to 12,518 in 1901. It has since doubled again.