Earliest evidence of human occupation includes stone tools made of Paleolithic chert, of the kind utilized by Stone Age people. Starting in approximately 200 CE, nomadic people from the coast began to settle the area, bringing their knowledge of metalworking (copper), ranching, agriculture, and weaving. These early settlers lived primarily along the Humanejos stream.
During the 4th and 5th centuries, the ranks of the local populations swelled to include newly arrived Celtic tribes from central Europe. The Celts brought with them various advanced technologies that included ironworking and fired ceramics. The local population was sustained mostly by ranching and agriculture.
Independent local development was interrupted by the arrival of the Carthagineans and Romans, the latter of whom recorded the history of the pre-Roman villages of the area. Local Roman artifacts include a number of grave markers and coins.
After the Battle of Guadalete (711), which signified the beginning of the Islamic conquest of Hispania, Parla and its inhabitants were a part of the territory governed by the Umayyad Caliphate. Parla once again appeared as an independent township during the Reconquista.
The territory was part of the Alfoz of Madrid, a Spanish medieval territorial designation for the land surrounding a village during the Reconquista. At the time, there were two major villages in the area: Parla, to the north, and Humanejos to the south. Humanejos disappeared around the year 1650.
The first document to reference Parla is a letter which King Alfonso XI of Castile wrote on 6 January 1338 in Trujillo, ceding control of the hamlet of Parla to the cardinal as payment for his help in the fight against the Moors. This document was later affirmed by King Peter of Castile on 7 December 1351.