Many old remains indicate an early occupation of the area: the menhir of Restournec, the underground rooms of Kerlouaver and Buberzot dating back to the iron-age, a Roman road at Hent-Guen and a Roman camp at Run-Faoen.
Similar to a parish of a city in 1486, Tréglamus was a branch of Pédernec. In 1790 it elected its first municipality.
Today, Tréglamus is a primarily an agricultural community.