The suspects are believed to have trafficked more than 560 people into Germany, and more than 300 migrants to Romania, federal police said.
The probe into the ring began after accounts were collected from Turkish and Syrian nationals in the border regions of Austria, Czech Republic and Poland.
The migrants were believed to have been brought to Germany via the so-called Balkans route.
They were allegedly forced to remain hidden among cargo in trucks “under inhumane conditions for several days” after being taken from Timisoara in Romania.
Four of the suspects were arrested in Romania by authorities who were searching properties used to house the migrants.
One suspect was picked up in Germany and another in Bulgaria.
During the raids, investigators said they secured evidence including three “high-value cars”, several mobile phones and cash.
Close to 200 officers were involved in the operation, including 130 in Germany alone. After a huge influx in 2015-2016, Germany has seen a renewed rise in the number of asylum seekers over the last year.
Chancellor Olaf Scholz’s government last month agreed tougher measures, including new partnerships with the countries of origin of new arrivals to take them back.