The former farming and fishing village on the Saale (185 m above sea level, 5 inhabitants), first mentioned in a document in 1417 as Nydernhasla, still had 115 inhabitants in 23 houses in 1787.

Frequent flooding of the Saale, especially the almost regular ice flooding after the snow melted in the low mountain range, hit Unterhasel hard. For this reason, the community of Unterhasel agreed to relocate to Kirchhasel on March 26, 1857. In 1914, the house of the Hein or Hammer family (formerly the "Kleiner Edelhof" estate), which had been earmarked for demolition, was moved to Rudolstadt as part of the future "Thuringian Farmhouses" museum of local history. Today, the settlement consists of only three farmsteads with 5 inhabitants, making it the smallest district in the municipality of Uhlstädt-Kirchhasel.

Unterhasel is the departure point for the Saale rafting tour. From here, the rafts set off on their two to three-hour trips to Weißen and Uhlstädt.