Mlačak families are Croats and they are mostly from Ozalj. In the past century, relatively most of Croatian residents bearing this family name were born in Karlovac and Ozalj.
Prevalence
About 60 people with faimily name Mlačak live in Croatia today, in 30 households. There were 100 of them in the middle of the past century, and their number decreased by 40 percent. They are located in 6 Croatian counties, in 7 cities and 5 other places, mostly in Karlovac (30), Zagreb (15), Sveticko Hrasce (<10), Mali Erjavec (<10), and in Ozalj (<5).
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.