Farum has existed for more than 1000 years. The name Farum refers to the founding fathers, sea merchants, who migrated from Bremen, Germany. At the time there was clear passage from the sea to Farum. This has since been filled with silt and by civic demands for more land. Around 1100, the community's first stone church was built: parts of it remain in the present church of Farum. In the 14th century, a damming project flooded the old ford and redirected much of the traffic bound for Copenhagen towards Fiskebæk, a short distance further south.
During recurrent wars with Sweden in the 17th century the area suffered enormous damage.
In 1800, the town was transferred from Copenhagen knight district to Frederiksborg County. Around this time, the economy of the area revived with renewed cultivation of the fertile agricultural land. Throughout the 19th century, the community expanded economically. In 1906, the community was linked to the capital by the railway between Copenhagen and Slangerup: in 1977, this became the Hareskovbanen radial of Copenhagen's S-train system.
In the early 1950s, the population was about 4000. Through the 1960s and 1970s, the community turned into a commuter town due to its proximity to Copenhagen and the population expanded past 10,000. By 1980, the population was over 16,000.
Today, Farum is divided into four parts: Farum West, Farum East, Farum North, and the Midpoint. Farum East and Farum West are separated by a highway that effectively divides the city. The Midpoint (Danish Midtpunktet) is a large complex of apartments built in a very special way. One-third of the population lives in these blocks, which house most of Farum's immigrants.