Archaeologists have discovered evidence of human settlement in the Kōfu area dating to the Japanese Paleolithic period, with continuous settlement through the Jōmon, Yayoi and Kofun periods. During the Nara period, the provincial temple of Kai Province was established in what is now Kōfu, indicating that the Nara period provincial capital was located nearby, as the name of the city implies. During the Heian period, a branch of the Minamoto clan, the “Kai-Genji” ruled over vast shōen estates, and developed a military force noted for its use of cavalry. By the Muromachi period, a branch of the Kai-Genji, the Takeda clan came to dominate the area, and built a castle in what is now part of Kōfu.
Under the rule of Takeda Nobutora, Kōfu was rebuilt as a castle town starting in 1519, and remained the capital of the Takeda clan under Takeda Shingen and his son Takeda Katsuyori.
During the Edo period, Kai Province was tenryō territory ruled directly by the Tokugawa shogunate, and Kōfu Castle remained its administrative center. Following the Meiji restoration, with the establishment of the municipalities system, the town of Kōfu was proclaimed on July 1, 1889.
During World War II, much of the city was destroyed by United States Army Air Forces B-29 Superfortress bombers during a major air raid during the night of 6 July 1945.
Kōfu is designated as one of the special cities of Japan. On March 1, 2006, Kōfu, with a population of 193,795, absorbed the town of Nakamichi (from Higashiyatsushiro District), and the northern part of the village of Kamikuishiki (from Nishiyatsushiro District) increasing the population to 201,184.