The helmet was discovered on 19 August 1864 at Barnaby Grange Farm, about 2 miles west of Guisborough town centre. It was found buried deep in a bed of gravel during road works carried out for the Cleveland Railway Company. The Reverend J.C. Atkinson described the circumstances of its discovery in an article for The Gentleman's Magazine in September 1864:
A short time since it was found expedient to supersede the existing accommodation-road to Barnaby Grange Farm, which crosses the Cleveland Railway on the level, by a new one carried beneath the line. While prosecuting the necessary excavation, and after reaching a depth of a few feet, a variety of [animal] bones, most of them in exceedingly good preservation, and with an abundance of earthy phosphate of iron investing them, were dug upon. These were carefully collected, and have now accumulated to a mass of considerable extent ... But the most remarkable of the non-osseus matters was a folded and doubled metal plate, embossed and engraved.
No other artefacts were found at the site and the bones appeared to have no connection with the helmet. They had apparently been deposited naturally by the prehistoric stream that had laid down the gravel bed. Atkinson noted that the artefact was in a strikingly good condition despite its obvious antiquity and the damage done to it:
Apart from the folding and doubling to which it has been subjected, it is in remarkably good preservation. It is scarcely corroded in any perceptible degree in any visible part, but is as bright as on the day it was consigned to its place of concealment. Neither is it bruised or dented, except where the workman's pick happened to strike; indeed, it is not even scratched.