The court identified them only as Radoslaw M, Lukasz M, and Pawel S, in keeping with Polish privacy laws.
Television footage from the court showed each man in turn expressing regret and acknowledging that stealing the sign was not a good idea.
The theft occurred in the night between December 17 and December 18, and the thieves left traces in the snow and then cut the sign into three pieces to make it easier to transport.
They also left behind the last letter "i" in the snow.
Acting on tips, police tracked down the sign in a snow-covered forest near the thieves' home on the other side of Poland, less than three days after it was stolen.
A Swedish man named Anders Hogstrom, is also a suspect and is detained in Sweden and due to be extradited to Poland. Two other Polish suspects remain imprisoned and under investigation.
Media reports have suggested that a British collector of Nazi memorabilia commissioned the theft, but police prosecutors have not confirmed that.
The slogan on the Auschwitz sign has come to be a potent symbol of Nazi Germany's atrocities during World War II and the Holocaust.
Between 1940 and 1945 more than one million people were killed in the gas chambers of Auschwitz-Birkenau or died of starvation or disease while forced to perform hard physical labour at the camp.