In Croatia, Topoljnjak families are Croats (from Pozega ). In the past century, relatively most of Croatian residents bearing this family name were born in Cakovec and in Serbia.
Prevalence
About 30 people with faimily name Topoljnjak live in Croatia today, in two households only. There were 20 of them in the middle of the past century, and their number increased by 50 percent. They are located in four Croatian cities only: in Pozega (<5), Zagreb (<5), Mihovljan (<5), and in Savudrija (<5).
Outside Croatia
Family name Topoljnjak is present in this form only in Croatia.
In the sources analysed in the project Acta Croatica so far, the name is mentioned over a hundred times, the first time 1902 in source Hartmann's General List of Apartments in Zagreb.