The ancient Baltic tribe Latgalians inhabited the territory of Kārsava since the 8th century. There are several hillforts near town.
In 1763 a Catholic church was built in Kārsava. The town was located near the Rēzekne-Ostrov postal road and it saw rapid development when the St. Petersburg-Vilnius railway line was constructed nearby and the town became a trading centre.
In 1935, on the eve of World War II, the population of Kārsava was 2,181, 37% of whom were Jewish.[3] The vast majority of them were murdered during the Holocaust.