In Croatia, Ostermann families are Croats (from Zagreb ). In the past century, relatively most of Croatian residents bearing this family name were born in Zagreb.
Prevalence
Only a few people with faimily name Ostermann live in Croatia today, in three households only. They are located in one Croatian city only, in Zagreb (<10).
Outside Croatia
Family name Ostermann is present in 39 countries worldwide. The family name "Ostermann " is used by some 10000 people in Germany , about 2000 in the United States , and some 1000 people in France.
In the sources analysed in the project Acta Croatica so far, the name is mentioned over five times, the first time 1917 in source List of Dignitaries, Officials and Public Servants of the Kingdom of Croatia-Slavonia.