Jeršek families are Croats and they are mostly from Zabok area. In the past century, relatively most of Croatian residents bearing this family name were born in Zabok area and in Osijek.
Prevalence
About 90 people with faimily name Jeršek live in Croatia today, in 30 households. There were 60 of them in the middle of the past century, and their number increased by 40 percent. They are located in 6 Croatian counties, four cities and 8 other places, mostly in Sveti Kriz Zacretje in Zabok area (30), Josipovac (25), Zagreb (15), Vrankovec in Zabok area (<10), and in Osijek (<10).
Outside Croatia
Family name Jeršek is present in five countries on three continents. The family name "Jersek " is used by small number of people in the United States and small number in Germany.
In the sources analysed in the project Acta Croatica so far, the name is mentioned few times, the first time 2007 in source Encyclopaedia of Croatian Surnames.