According to the EFE news agency, Steinmeier told Barzani on the sidelines of the Munich Security Conference that the referendum would "only feed new conflicts" in the region.
The top German diplomat reportedly made it clear that the country had the same attitude towards any border changes in Syria and Iraq.
In 2014, Barzani urged the parliament of the autonomous region to identify a date for a referendum on independence. Barzani called Baghdad's politics a failure that has allowed the Islamic State militant group to approach Kurdish borders.
Kurds are a Middle Eastern ethnic group with the population of some 30-35 million living mainly in Turkey, Iran, Iraq and Syria.