Written sources mention Radotín as early as in 993, when a tithe of the local farm yard belonged to the just-founded Benedictine monastery in Břevnov. Later on, until the Hussite wars the town was kept by friars from the Cistercian monastery in Zbraslav, on the opposite bank of the river Berounka, as well as during 1536-1785.
The citizens of Radotín got the right to call it town in 1968 and three years later the previous Local National Committee accepted the municipal coat-of-arms. It was a blue shield, in whose lower part there is a water surface ruffled with waves and there is a silver town fortification of blocks with six walls standing out of it. Above the wall in the upper part of the shield there is a silver cog wheel. That symbolizes advanced industry and water waves over the river of Berounka.
The natural centre of Radotín is formed by the Square of Horymír. On the west it is bounded with very important railway line Beroun-Zdice-Plzeň-Cheb. Since 1915 the square was called the Square of Žižka, in the honour of the fabled Hussite commander Jan Žižka of Trocnov. During 1928-1932 it was renamed the Square of Fügner, after the co-founder of Sokol, Jindřich Fügner; and then the name Square of Horymír was back for sixteen years. During the communist regime the official name was the Square of 25th February, in memory of the revolution in 1948. But tradition is a tradition and thus the name of Square of Horymír has been returned in 1992.
According to a legend, mythical Czech prince Horymír of Neumětely saved himself from execution of the death sentence for destroying the mines in Březové Hory by the action when he jumped over the fortifications of Vyšehrad on his faithful horse Šemík, they swam over the river of Vltava together and they got to Neumětely through Smíchov and Zlíchov. According to the legend Šemík was running, with his master in the saddle, around Radotín and both of them drank water from the local stream. Šemík had become so exhausted on the way that he paid his life for saving his master.