Although there is evidence of inhabiting the area since Roman times (coins, tombstones, bricks printed with the stamp of the XIII Gemina Legion), however, the first documentary evidence dates from 1373 under the name Zârna. In 1395 the town is mentioned as "possession regalis Zerne", its name varying throughout history as Villa Czerne or Zernyest.
In the 13th and 14th centuries, marked by the colonization of the Saxons in Transylvania, a documentary attestation also appears in Tohan (1294) under the name Tuhan. The locality also appears in documents from 1731, which mention the existence of a Romanian school, and in 1769 the Tohanul Nou is also documented.
The most important historical events are related to the battle of Zărnești (1690), when the last Ottoman incursion into Transylvania took place, or to the participation in the War of Independence (1877-1878).
The main occupations of the inhabitants were represented by silvo-pastoral activities, agriculture, hauling, the industrialization process of the town starting at the beginning of the 19th century with the establishment of the first manufactures, leading to the first factories, paper industry (1852) or armament industry (1936).
Since 1951, Zărnești has become a city, developing a lot from an industrial and urban point of view.
Among the local personalities, the best known are: Bartolomeu Baiulescu (1831-1909) - teacher, priest and publicist, Ioan Mețianu (1828-1916) - Metropolitan of Transylvania, founder of the “Astra” Society, Dr. Ioan Șenchea (1864-1916 ) - famous jurist, Gen. Traian Moșoiu (1868-1932) - Minister of War, Dr. Caius Tiberiu Spârchez (1899-1977) - academician, creator of the Romanian school of gastroenterology.
Currently, the city is on the rise, tourism is developing, and the tourist destination Zărnești-Piatra Craiului is becoming a landmark of Romanian and European tourism.