The police used a new Child Alert system for the first time to find Maja, who disappeared Tuesday from northwestern Poland, according to police spokesman Mariusz Sokolowski.
"Maja is safe and sound. She was found in a car with her abductor along the side of a highway in Germany," near the town of Friedland some 80 kilometres (50 miles) from the Polish border, Sokolowski told reporters.
He said the man was possibly mentally unstable and had earlier been convicted in Britain of abducting a 9-year-old child. He refused to reveal the man's name and nationality.
Maja's father alerted the police after she failed to return home from school.
Officers from both sides of the border searched for an Opel Vectra car with a Polish licence plate, which surveillance cameras recorded near Maja's house in the village of Wolczkowo, a couple of kilometres from the German border.
Police used the national Child Alert system, introduced in Poland in late 2013, as well as the Amber Alert Europe system to notably put out word about the missing girl.