The origins of Bytów can be traced back to the early Middle Ages when there existed a stronghold at the place of today’s town. Bytów was mentioned, under the Latin name castrum nomine Bitom, by Gallus Anonymus in his Chronicles. The stronghold was situated approximately 500 meters westward from today’s castle and was called “Smolarnia” (“a tar place”). The town was probably named after its founder - Byt. The oldest record with the name of the town contains the form “Butow” and comes from 1321 when Bytów became the property of the von Behr family from Western Pomerania.

The Order of the Teutonic Knights bought these lands, the town and the stronghold eight years later. It is estimated that the parish in Bytów was established in 1335. Consequantly, the parish became one of the oldest in the Pomerania region. Bytów was granted Chełmno law on 12.07.1246. The town had its own government and mayor, as well as judiciary and a coat of arms which has not changed until today. The town was located away from buildings which had already existed. The event which had an enormous impact on the history of Bytów was building a defensive castle which was located at the end of the 14th century. The castle replaced the old stronghold of the von Behr family. The castle was a seat of officials of the Teutonic Knights and the Western watchtower of the Order. During the Thirteen Years' War (1454-1466) owners of Bytów often changed.

Eventually, Casimir IV Jagiellon (Kazimierz IV Jagiellończyk) granted the town to Eric II, Duke of Pomerania, as a perpetual fiefdom. Lębork was another town granted to Eric II. Both towns and their lands were called a Lębork-Bytów fiefdom. After Duke Eric II had died, Bytów did not become a part of Poland. This situation did not meet with acceptance from inhabitants of Royal Prussia and Gdańsk. Regaining Bytów was not successful for several decades until 1526, when the town became a fiefdom of Poland and was administered by Pomeranian Dukes from the Gryfit dynasty. After the death of Bogislaw XIV, Duke of Pomerania (Bogusław XIV), who was the last male successor of the dynasty, Bytów was again under the Polish rule. It happened in 1637 and lasted for following 20 years. However, Poland was weakened after the war against Sweden and Treaty of Bromberg took place in 1657. As a result of the treaty, lands of Bytów and Lębork were granted as a fief to Elector of Brandenburg from the Hohenzollern dynasty.

This state was legally valid until 1773 but the fief was practically not renewed until the end of the 17th century [1.1]. On 18.09.1773, Polish king Stanisław August Poniatowski and king Frederick II of Prussia signed a treaty in Warsaw. According to the treaty, Poland renounced the rights to Lębork-Bytów fiefdom. Fires and bubonic plague wreaked havoc in Bytów in the 18th century [1.2]. The town was under the German (or more specifically: Brandenburgian and Prussian) rule until 1945. Poles constituted approximately 15% of total population of Bytów County in 1912. In consequence of the Treaty of Versailles, Bytów was still a part of Germany. However, Polish organizations were active in the town which was again (after 288 years) within the borders of Poland in 1945. On 08.03.1945 Bytów was occupied by the Red Army.

Approximately 55-65% of the town was destroyed during warfare. First Polish authorities started to administer the town in April and Bytów started to be slowly rebuilt. Throughout its whole history, Bytów was a multiethnic town – Kashubians, Poles and Germans lived here until 1945 and Jews until the 1930s. As a result of treaties signed after the end of the Second World War, Bytów belonged to Poland. German citizens, who constituted the largest part of total town population, had to leave Bytów. The town was populated by Polish people, also those from Kresy (Polish eastern frontier) and Kashubia. Moreover, Ukrainians from “Operation Vistula” (forced deportation of southeastern post-war Poland's Ukrainians) came here after 1947.