The car had seven seats, but 23 people got out: A Swiss customs officer on the border with Germany near Weil am Rhein was surprised when he checked the car.
The vehicle, a Seat Alhambra, contained nine adults and 14 children.
The customs officer refused entry and informed the German police.
The extended family then said they wanted to travel to Bern, the Freiburg police said on Tuesday.
The driver, who lives in Switzerland, must now expect a fine because he has transported several people without adequate security.
After the check was completed, the family was allowed to enter Switzerland on Monday – but not all together in one car, as a police spokesman emphasized.
him/dpa