Hillfields was originally known as Harnall and was a district under the Holy Trinity Parish. Harnall was first mentioned in Coombe Abbey Charter as being in the ownership of the Prior's Half of Coventry in the 12th century. It was again mentioned in the 12th century in a passage noting a road that lead "through the middle of Harnall along the country of Stoke". In the 13th century, Harnall was owned by Roger de Montalt and was one of his estates consisting of little more than cottages and crofts. Before this, the Coventry Priory had owned land in Harnall.
In 1542, the land was given by the Priory to the Corporation, and in 1551 the Prior's Orchard with Swans Pool, New Pool, Harnall Field and other land were included in the endowment of Sir Thomas White's Charity. In 1632, Prior's Orchard Mill, located near Springfield Brook and Swanswell Pool, was absorbed into Swanswell Waterworks. The waterworks produced water for Coventry.
In 1816, the first school in the area is recorded as being located within Primrose Hill House, which had been converted to serve as a school. This closed in 1837; however, it was reopened as a boarding school in 1848 by Rev. J. S. Gilbert and T. Wyles.
In 1828, Harnall became the first suburb in Coventry after the city expanded outside the city walls. This resulted in the construction of villas throughout the suburb. It became known as New Town. Problems arose soon after its incorporation into Coventry when the River Sherbourne, which separated the two areas, began to flood as a result of two mills. These two mills were finally removed in 1844 by an Act of Parliament. Once the two mills were removed, New Town could develop and connect to Coventry.
The Health of Towns Act 1848 resulted in the establishment of a Local Board of Health in 1849 who then surveyed the city in 1850. A result of the survey was new building guidelines for the city. As much of the city had already been developed, Hillfields became a favourable location for new houses and the area began to expand. Also, the standard of living in Hillfields was much higher than those who remained in the slums within Coventry city.